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LT1762 Series 150mA, Low Noise, LDO Micropower Regulators
U
Dropout Voltage
400 350 20 40 60 80 100 120 140 160 OUTPUT CURRENT (mA)
1762 TA02
FEATURES
s s s s s s s s s s s
DESCRIPTIO
s s s s
Low Noise: 20VRMS (10Hz to 100kHz) Low Quiescent Current: 25A Wide Input Voltage Range: 1.8V to 20V Output Current: 150mA Very Low Shutdown Current: < 1A Low Dropout Voltage: 300mV No Protection Diodes Needed Fixed Output Voltages: 2.5V, 3V, 3.3V, 5V Adjustable Output from 1.22V to 20V Stable with 2.2F Output Capacitor Stable with Aluminum, Tantalum or Ceramic Capacitors Reverse Battery Protection No Reverse Current Overcurrent and Overtemperature Protected 8-Lead MSOP Package
APPLICATIO S
s s s s
Cellular Phones Battery-Powered Systems Frequency Synthesizers Noise-Sensitive Instrumentation Systems
The LT (R)1762 series are micropower, low noise, low dropout regulators. The devices are capable of supplying 150mA of output current with a dropout voltage of 300mV. Designed for use in battery-powered systems, the low 25A quiescent current makes them an ideal choice. Quiescent current is well controlled; it does not rise in dropout as it does with many other regulators. A key feature of the LT1762 regulators is low output noise. With the addition of an external 0.01F bypass capacitor, output noise drops to 20VRMS over a 10Hz to 100kHz bandwidth. The LT1762 regulators are stable with output capacitors as low as 2.2F. Small ceramic capacitors can be used without the series resistance required by other regulators. Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The parts come in fixed output voltages of 2.5V, 3V, 3.3V and 5V, and as an adjustable device with a 1.22V reference voltage. The LT1762 regulators are available in the 8-lead MSOP package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
3.3V Low Noise Regulator
DROPOUT VOLTAGE (mV)
300 250 200 150 100 50 0 0
VIN 3.7V TO 20V
IN 1F
OUT SENSE LT1762-3.3 0.01F
SHDN BYP GND
U
U
+
3.3V AT 150mA 20VRMS NOISE 10F
1762 TA01
1
LT1762 Series
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW OUT SENSE/ADJ* BYP GND 1 2 3 4 8 7 6 5 IN NC NC SHDN
IN Pin Voltage ........................................................ 20V OUT Pin Voltage .................................................... 20V Input to Output Differential Voltage ....................... 20V SENSE Pin Voltage ............................................... 20V ADJ Pin Voltage ...................................................... 7V BYP Pin Voltage.................................................... 0.6V SHDN Pin Voltage ................................................. 20V Output Short-Circut Duration .......................... Indefinite Operating Junction Temperature Range (Note 2) ............................................ - 40C to 125C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LT1762EMS8 LT1762EMS8-2.5 LT1762EMS8-3 LT1762EMS8-3.3 LT1762EMS8-5 MS8 PART MARKING LTHF LTHG LTHH LTHJ LTHK
MS8 PACKAGE 8-LEAD PLASTIC MSOP
*PIN 2: SENSE FOR LT1762-2.5/ LT1762-3/LT1762-3.3/LT1762-5 ADJ FOR LT1762
TJMAX = 150C, JA = 125C/ W SEE THE APPLICATIONS INFORMATION SECTION.
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. (Note 2)
PARAMETER Minimum Operating Voltage Regulated Output Voltage (Note 4) CONDITIONS ILOAD = 150mA LT1762-2.5 VIN = 3V, ILOAD = 1mA 3.5V < VIN < 20V, 1mA < ILOAD < 150mA LT1762-3 VIN = 3.5V, ILOAD = 1mA 4V < VIN < 20V, 1mA < ILOAD < 150mA
q q q q q q q q q q q q
MIN 2.475 2.435 2.970 2.925 3.267 3.220 4.950 4.875 1.208 1.190
TYP 1.8 2.5 2.5 3 3 3.3 3.3 5 5 1.22 1.22 1 1 1 1 1 4 4
MAX 2.3 2.525 2.565 3.030 3.075 3.333 3.380 5.050 5.125 1.232 1.250 5 5 5 5 5 12 25 15 30 17 33 25 50 6 12
UNITS V V V V V V V V V V V mV mV mV mV mV mV mV mV mV mV mV mV mV mV mV
LT1762-3.3 VIN = 3.8V, ILOAD = 1mA 4.3V < VIN < 20V, 1mA < ILOAD < 150mA LT1762-5 ADJ Pin Voltage (Notes 3, 4) Line Regulation LT1762 VIN = 5.5V, ILOAD = 1mA 6V < VIN < 20V, 1mA < ILOAD < 150mA VIN = 2V, ILOAD = 1mA 2.3V < VIN < 20V, 1mA < ILOAD < 150mA VIN = 3V to 20V, ILOAD = 1mA VIN = 3.5V to 20V, ILOAD = 1mA VIN = 3.8V to 20V, ILOAD = 1mA VIN = 5.5V to 20V, ILOAD = 1mA VIN = 2V to 20V, ILOAD = 1mA VIN = 3.5V, ILOAD = 1mA to 150mA VIN = 3.5V, ILOAD = 1mA to 150mA VIN = 4V, ILOAD = 1mA to 150mA VIN = 4V, ILOAD = 1mA to 150mA VIN = 4.3V, ILOAD = 1mA to 150mA VIN = 4.3V, ILOAD = 1mA to 150mA VIN = 6V, ILOAD = 1mA to 150mA VIN = 6V, ILOAD = 1mA to 150mA VIN = 2.3V, ILOAD = 1mA to 150mA VIN = 2.3V, ILOAD = 1mA to 150mA
LT1762-2.5 LT1762-3 LT1762-3.3 LT1762-5 LT1762 (Note 3) LT1762-2.5 LT1762-3 LT1762-3.3 LT1762-5 LT1762 (Note 3)
Load Regulation
q
5
q
9
q
1
q
2
U
W
U
U
WW
W
LT1762 Series
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. (Note 2)
PARAMETER Dropout Voltage VIN = VOUT(NOMINAL) (Notes 5, 6) CONDITIONS ILOAD = 1mA ILOAD = 1mA ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 150mA ILOAD = 150mA GND Pin Current VIN = VOUT(NOMINAL) (Notes 5, 7) ILOAD = 0mA ILOAD = 1mA ILOAD = 10mA ILOAD = 50mA ILOAD = 150mA COUT = 10F, CBYP = 0.01F, ILOAD = 150mA, BW = 10Hz to 100kHz (Notes 3, 8) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 20V VIN = 6V, VSHDN = 0V VIN - VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 150mA VIN = 7V, VOUT = 0V VIN = VOUT(NOMINAL) + 1V, VOUT = - 0.1V VIN = - 20V, VOUT = 0V LT1762-2.5 LT1762-3 LT1762-3.3 LT1762-5 LT1762 (Note 3) VOUT = 2.5V, VIN < 2.5V VOUT = 3V, VIN < 3V VOUT = 3.3V, VIN < 3.3V VOUT = 5V, VIN < 5V VOUT = 1.22V, VIN < 1.22V
q q q q q
MIN
TYP 0.09 0.15
MAX 0.15 0.19 0.21 0.25 0.27 0.31 0.33 0.40 65 120 500 1.8 7 100 2
UNITS V V V V V V V V A A A mA mA VRMS nA V V A A
q
0.21
q
0.27
q q q q q q
25 70 350 1.3 4 20 30 0.25 0.8 0.65 0.1 1 0.1 50 65 300 160
Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 9) Quiescent Current in Shutdown Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 10)
1
A dB mA mA
1 10 10 10 10 5 20 20 20 20 10
mA A A A A A
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1762 regulators are tested and specified under pulse load conditions such that TJ TA. The LT1762 is 100% tested at 25C. Performance at - 40C and 125C is assured by design, characterization and correlation with statistical process controls. Note 3: The LT1762 (adjustable version) is tested and specified for these conditions with the ADJ pin connected to the OUT pin. Note 4: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current, the input voltage range must be limited. Note 5: To satisfy requirements for minimum input voltage, the LT1762 (adjustable version) is tested and specified for these conditions with an
external resistor divider (two 250k resistors) for an output voltage of 2.44V. The external resistor divider will add a 5A DC load on the output. Note 6: Dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified output current. In dropout, the output voltage will be equal to: VIN - VDROPOUT. Note 7: GND pin current is tested with VIN = VOUT(NOMINAL) and a current source load. This means the device is tested while operating in its dropout region. This is the worst-case GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 8: ADJ pin bias current flows into the ADJ pin. Note 9: SHDN pin current flows into the SHDN pin. Note 10: Reverse output current is tested with the IN pin grounded and the OUT pin forced to the rated output voltage. This current flows into the OUT pin and out the GND pin.
3
LT1762 Series TYPICAL PERFORMANCE CHARACTERISTICS
Typical Dropout Voltage
500 450
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
400 350 300 250 200 150 100 50 0 0 20 40 60 80 100 120 140 160 LOAD CURRENT (mA)
1762 G01
TJ = 125C
TJ = 25C
Quiescent Current
40 35
QUIESCENT CURRENT (A)
VIN = 6V RL = , IL = 0 (LT1762-2.5/-3/-3.3/-5) RL = 250k, IL = 5A (LT1762)
OUTPUT VOLTAGE (V)
25 20 15 10 5 0 -50 -25 0 25 50 75 100 125 VSHDN = VIN
2.51 2.50 2.49 2.48 2.47 2.46 -50 -25 0 25 50 75 100 125
OUTPUT VOLTAGE (V)
30
TEMPERATURE (C)
1762 G04
LT1762-3.3 Output Voltage
3.360 IL = 1mA 3.345
OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V)
3.315 3.300 3.285 3.270 3.255 3.240 -50 -25 0 25 50 75 100 125
5.025 5.000 4.975 4.950 4.925 4.900 -50 -25 0 25 50 75 100 125
ADJ PIN VOLTAGE (V)
3.330
TEMPERATURE (C)
1762 G07
4
UW
Guaranteed Dropout Voltage
500 450 400 350 300 250 200 150 100 50 0 0 20 40 60 80 100 120 140 160 LOAD CURRENT (mA)
1762 G02
Dropout Voltage
500 450
= TEST POINTS TJ 125C
400 350 300 250 200 150 100 50 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125 IL = 1mA IL = 50mA IL = 10mA IL = 150mA
TJ 25C
1762 G03
LT1762-2.5 Output Voltage
2.54 IL = 1mA 2.53 2.52 3.045 3.030 3.015 3.000 2.985 2.970 2.955 3.060
LT1762-3 Output Voltage
IL = 1mA
2.940 -50 -25
0
25
50
75
100
125
TEMPERATURE (C)
1762 G05
TEMPERATURE (C)
1762 G06
LT1762-5 Output Voltage
5.100 IL = 1mA 5.075 5.050 1.235 1.230 1.225 1.220 1.215 1.210 1.205 1.240
LT1762 ADJ Pin Voltage
IL = 1mA
1.200 -50 -25
0
25
50
75
100
125
TEMPERATURE (C)
1762 G08
TEMPERATURE (C)
1762 G09
LT1762 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1762-2.5 Quiescent Current
400 350 TJ = 25C RL =
QUIESCENT CURRENT (A)
QUIESCENT CURRENT (A)
300 250 200 150 100 50 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 VSHDN = VIN VSHDN = 0V
QUIESCENT CURRENT (A)
LT1762-5 Quiescent Current
400 350 TJ = 25C RL =
QUIESCENT CURRENT (A)
30 25 20 15 10 5
QUIESCENT CURRENT (A)
GND PIN CURRENT (A)
300 250 200 150 VSHDN = VIN 100 50 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 VSHDN = 0V
LT1762-3 GND Pin Current
800 700 TJ = 25C VIN = VSHDN *FOR VOUT = 3V 800 700
GND PIN CURRENT (A)
GND PIN CURRENT (A)
GND PIN CURRENT (A)
600 500 400 300 200 100 0 0 1
RL = 120 IL = 25mA*
RL = 300 IL = 10mA*
RL = 3k IL = 1mA* 2 34567 INPUT VOLTAGE (V) 8 9 10
UW
1762 G10 1762 G13 1762 G16
LT1762-3 Quiescent Current
400 350 300 250 200 150 100 50 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 VSHDN = VIN VSHDN = 0V TJ = 25C RL = 400 350 300 250 200 150 100 50 0
LT1762-3.3 Quiescent Current
TJ = 25C RL =
VSHDN = VIN 0 1 2
VSHDN = 0V
34567 INPUT VOLTAGE (V)
8
9
10
1762 G11
1762 G12
LT1762 Quiescent Current
800
VSHDN = VIN
LT1762-2.5 GND Pin Current
700 600 500 400 300 200 100 RL = 2.5k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 RL = 100 IL = 25mA* RL = 250 IL = 10mA* TJ = 25C VIN = VSHDN *FOR VOUT = 2.5V
TJ = 25C RL = 250k
VSHDN = 0V 0 0 2 4 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V)
1762 G14
0
1762 G15
LT1762-3.3 GND Pin Current
TJ = 25C VIN = VSHDN *FOR VOUT = 3.3V
LT1762-5 GND Pin Current
800 700 600 500 400 300 200 100
8 9 10
600 500 400 300 200 100 0 0 1 2
RL = 132 IL = 25mA*
RL = 200 IL = 25mA* TJ = 25C VIN = VSHDN *FOR VOUT = 5V
RL = 330 IL = 10mA*
RL = 3.3k IL = 1mA* 34567 INPUT VOLTAGE (V)
RL = 5k IL = 1mA*
RL = 500 IL = 10mA*
0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1762 G17
1762 G18
5
LT1762 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1762 GND Pin Current
800 700 TJ = 25C VIN = VSHDN *FOR VOUT = 1.22V
GND PIN CURRENT (mA)
GND PIN CURRENT (A)
600 500 400 300 200 100 0 0 1
RL = 48.8 IL = 25mA*
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
GND PIN CURRENT (mA)
RL = 122 IL = 10mA*
RL = 1.22k IL = 1mA* 2 34567 INPUT VOLTAGE (V) 8 9 10
LT1762-3.3 GND Pin Current
5.0 4.5
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 2 RL = 33 IL = 100mA* RL = 66 IL = 50mA* RL = 22 IL = 150mA*
TJ = 25C VIN = VSHDN *FOR VOUT = 3.3V
34567 INPUT VOLTAGE (V)
GND Pin Current vs ILOAD
5.0 4.5
GND PIN CURRENT (mA)
VIN = VOUT(NOMINAL) + 1V
SHDN PIN THRESHOLD (V)
SHDN PIN THRESHOLD (V)
4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 20 40 60 80 100 120 140 160 OUTPUT CURRENT (mA)
1762 G25
6
UW
1762 G19
LT1762-2.5 GND Pin Current
5.0 4.5 4.0 RL = 16.7 IL = 150mA* TJ = 25C VIN = VSHDN *FOR VOUT = 2.5V 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
LT1762-3 GND Pin Current
TJ = 25C VIN = VSHDN *FOR VOUT = 3V RL = 20 IL = 150mA*
RL = 25 IL = 100mA* RL = 50 IL = 50mA*
RL = 30 IL = 100mA* RL = 60 IL = 50mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1762 G20
1762 G21
LT1762-5 GND Pin Current
5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 8 9 10 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 RL = 50 IL = 100mA* RL = 100 IL = 50mA* TJ = 25C VIN = VSHDN *FOR VOUT = 5V RL = 33.3 IL = 150mA* 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0
LT1762 GND Pin Current
TJ = 25C VIN = VSHDN *FOR VOUT = 1.22V RL = 8.07 IL = 150mA* RL = 12.2 IL = 100mA* RL = 24.4 IL = 50mA*
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
1762 G22
1762 G23
1762 G24
SHDN Pin Threshold (On-to-Off)
1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -50 -25 50 0 75 25 TEMPERATURE (C) 100 125 IL = 1mA
1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1
SHDN Pin Threshold (Off-to-On)
IL = 150mA
IL = 1mA
0 -50 -25
50 0 75 25 TEMPERATURE (C)
100
125
1762 G26
1762 G27
LT1762 Series TYPICAL PERFORMANCE CHARACTERISTICS
SHDN Pin Input Current
1.4
SHDN PIN INPUT CURRENT (mA) SHDN PIN INPUT CURRENT (A)
1.6 VSHDN = 20V 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -50 -25 0 25 50 75 100 125
1.2 1.0 0.8 0.6 0.4 0.2 0
ADJ PIN BIAS CURRENT (nA)
0
1
2
345678 SHDN PIN VOLTAGE (V)
Current Limit
500 450
SHORT-CIRCUIT CURRENT (mA)
VOUT = 0V
SHORT-CIRCUIT CURRENT (mA)
400 350 300 250 200 150 100 50 0 0 1 4 3 2 5 INPUT VOLTAGE (V) 6 7
1762 G31
400 350 300 250 200 150 100 50 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125
REVERSE OUTPUT CURRENT (A)
Reverse Output Current
30
REVERSE OUTPUT CURRENT (A)
25 20 15
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
VIN = 0V VOUT = 1.22V (LT1762) VOUT = 2.5V (LT1762-2.5) VOUT = 3V (LT1762-3) VOUT = 3.3V (LT1762-3.3) VOUT = 5V (LT1762-5)
LT1762-2.5/-3/-3.3/-5 10 LT1762 5 0 -50 -25
50 25 0 75 TEMPERATURE (C)
UW
9
1762 G28
SHDN Pin Input Current
140 120 100 80 60 40 20
ADJ Pin Bias Current
10
0 -50 -25
TEMPERATURE (C)
1762 G29
50 25 0 75 TEMPERATURE (C)
100
125
1762 G30
Current Limit
500 450 VIN = 7V VOUT = 0V
100 90 80 70 60 50 40 30 20 10 0
Reverse Output Current
TJ = 25C, VIN = 0V CURRENT FLOWS INTO OUTPUT PIN VOUT = VSENSE (LT1762-2.5/-3/-3.3/-5) VOUT = VADJ (LT1762) LT1762-2.5 LT1762-3
LT1762
LT1762-3.3 LT1762-5 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10
1762 G32
1762 G33
Input Ripple Rejection
80 70 60 50 40 30 20 10 0 10 IL = 150mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE CBYP = 0 100 COUT = 2.2F COUT = 10F 80 70 60 50 40 30 20 10 0 1k 10k FREQUENCY (Hz) 100k 1M
1762 G35
Input Ripple Rejection
CBYP = 0.01F
CBYP = 1000pF CBYP = 100pF
IL = 150mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE COUT = 10F 10 100 1k 10k FREQUENCY (Hz) 100k 1M
1762 G36
100
125
1762 G34
7
LT1762 Series TYPICAL PERFORMANCE CHARACTERISTICS
Ripple Rejection
68 66
MINIMUM INPUT VOLTAGE (V)
RIPPLE REJECTION (dB)
64 62 60 58 56 54 VIN = VOUT (NOMINAL) + 1V + 0.5VP-P RIPPLE AT f = 120Hz IL = 150mA 0 25 50 75 100 125
LOAD REGULATION (mV)
52 -50 -25
TEMPERATURE (C)
1762 G37
Output Noise Spectral Density CBYP = 0
OUTPUT NOISE SPECTRAL DENSITY (V/Hz) OUTPUT NOISE SPECTRAL DENSITY (V/Hz)
10 COUT = 10F IL = 150mA LT1762-5 1 LT1762-2.5 LT1762 0.1 LT1762-3 LT1762-3.3
0.01 10
100
RMS Output Noise vs Bypass Capacitor
160 140 LT1762-5 COUT = 10F IL = 150mA f = 10Hz TO 100kHz LT1762-3.3 100 80 60 40 LT1762-2.5 20 0 10 100 CBYP (pF)
1762 G42
OUTPUT NOISE (VRMS)
OUTPUT NOISE (VRMS)
120 LT1762-3
LT1762
8
UW
LT1762 Minimum Input Voltage
2.50 2.25 2.00 1.75 1.50 1.25 1.00 0.75 0.50 0.25 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125 IL = 1mA VOUT = 1.22V
0 5
Load Regulation
LT1762 LT1762-3
IL = 150mA
-5 -10 -15 -20 VIN = VOUT(NOMINAL) + 1V IL = 1mA TO 150mA 0 25 50
LT1762-2.5 LT1762-3.3 LT1762-5
-25 -50 -25
75
100
125
TEMPERATURE (C)
1762 G38
1762 G39
Output Noise Spectral Density
10 COUT = 10F IL = 150mA LT1762-5 1 CBYP = 100pF LT1762 CBYP = 1000pF
0.1
CBYP = 0.01F
1k 10k FREQUENCY (Hz)
100k
1762 G40
0.01 10
100
1k 10k FREQUENCY (Hz)
100k
1762 G41
RMS Output Noise vs Load Current (10Hz to 100kHz)
160 140 120 100 80 60 40 20 1000 10000 0 0.01 0.1 LT1762-5 LT1762 10 100 1 LOAD CURRENT (mA) 1000
1762 G43
COUT = 10F CBYP = 0 CBYP = 0.01F
LT1762-5
LT1762
LT1762 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1762-5 10Hz to 100kHz Output Noise CBYP = 0 LT1762-5 10Hz to 100kHz Output Noise CBYP = 100pF
VOUT 100V/DIV
COUT = 10F IL = 150mA
LT1762-5 10Hz to 100kHz Output Noise CBYP = 1000pF
VOUT 100V/DIV
COUT = 10F IL = 150mA
LT1762-5 Transient Response CBYP = 0
0.3 OUTPUT VOLTAGE DEVIATION (V)
OUTPUT VOLTAGE DEVIATION (V)
0.2 0.1 0 -0.1 -0.2 -0.3
LOAD CURRENT (mA)
LOAD CURRENT (mA)
150 100 50 0 0 400 800 1200 TIME (s) 1600 2000
1762 G48
UW
1ms/DIV 1ms/DIV
VOUT 100V/DIV
1ms/DIV
1762 G44
COUT = 10F IL = 150mA
1762 G45
LT1762-5 10Hz to 100kHz Output Noise CBYP = 0.01F
VOUT 100V/DIV
1ms/DIV
1762 G46
COUT = 10F IL = 150mA
1762 G47
LT1762-5 Transient Response CBYP = 0.01F
VIN = 6V CIN = 10F COUT = 10F 0.04 0.02 0 -0.02 -0.04 VIN = 6V CIN = 10F COUT = 10F
150 100 50 0 0 40 80 120 TIME (s) 160 200
1762 G49
9
LT1762 Series
PIN FUNCTIONS
OUT (Pin 1): Output. The output supplies power to the load. A minimum output capacitor of 2.2F is required to prevent oscillations. Larger output capacitors will be required for applications with large transient loads to limit peak voltage transients. See the Applications Information section for more information on output capacitance and reverse output characteristics. SENSE (Pin 2): Output Sense. For fixed voltage versions of the LT1762 (LT1762-2.5/LT1762-3/LT1762-3.3/ LT1762-5), the SENSE pin is the input to the error amplifier. Optimum regulation will be obtained at the point where the SENSE pin is connected to the OUT pin of the regulator. In critical applications, small voltage drops are caused by the resistance (RP) of PC traces between the regulator and the load. These may be eliminated by connecting the SENSE pin to the output at the load as shown in Figure 1 (Kelvin Sense Connection). Note that the voltage drop across the external PC traces will add to the dropout voltage of the regulator. The SENSE pin bias current is 10A at the nominal rated output voltage. The SENSE pin can be pulled below ground (as in a dual supply system where the regulator load is returned to a negative supply) and still allow the device to start and operate. ADJ (Pin 2): Adjust. For the adjustable LT1762, this is the input to the error amplifier. This pin is internally clamped to 7V. It has a bias current of 30nA which flows into the pin (see curve of ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics). The ADJ pin voltage is 1.22V referenced to ground and the output voltage range is 1.22V to 20V. BYP (Pins 3): Bypass. The BYP pin is used to bypass the reference of the LT1762 regulators to achieve low noise performance from the regulator. The BYP pin is clamped internally to 0.6V (one VBE). A small capacitor from the output to this pin will bypass the reference to lower the output voltage noise. A maximum value of 0.01F can be used for reducing output voltage noise to a typical 20VRMS over a 10Hz to 100kHz bandwidth. If not used, this pin must be left unconnected. GND (Pin 4): Ground. SHDN (Pin5): Shutdown. The SHDN pin is used to put the LT1762 regulators into a low power shutdown state. The output will be off when the SHDN pin is pulled low. The SHDN pin can be driven either by 5V logic or opencollector logic with a pull-up resistor. The pull-up resistor is required to supply the pull-up current of the opencollector gate, normally several microamperes, and the SHDN pin current, typically 1A. If unused, the SHDN pin must be connected to VIN. The device will be in low power shutdown state if the SHDN pin is not connected. IN (Pin 8): Input. Power is supplied to the device through the IN pin. A bypass capacitor is required on this pin if the device is more than six inches away from the main input filter capacitor. In general, the output impedance of a battery rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 1F to 10F is sufficient. The LT1762 regulators are designed to withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reverse input, which can happen if a battery is plugged in backwards, the device will act as if there is a diode in series with its input. There will be no reverse current flow into the regulator and no reverse voltage will appear at the load. The device will protect both itself and the load.
RP
10
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8
IN LT1762
OUT
1
+
VIN
5
SHDN
SENSE GND 4
2
+
LOAD
RP
1762 F01
Figure 1. Kelvin Sense Connection
LT1762 Series
APPLICATIONS INFORMATION
The LT1762 series are 150mA low dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 150mA at a dropout voltage of 300mV. Output voltage noise can be lowered to 20VRMS over a 10Hz to 100kHz bandwidth with the addition of a 0.01F reference bypass capacitor. Additionally, the reference bypass capacitor will improve transient response of the regulator, lowering the settling time for transient load conditions. The low operating quiescent current (25A) drops to less than 1A in shutdown. In addition to the low quiescent current, the LT1762 regulators incorporate several protection features which make them ideal for use in battery-powered systems. The devices are protected against both reverse input and reverse output voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT1762-X acts like it has a diode in series with its output and prevents reverse current flow. Additionally, in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 20V and still allow the device to start and operate. Adjustable Operation The adjustable version of the LT1762 has an output voltage range of 1.22V to 20V. The output voltage is set by the ratio of two external resistors as shown in Figure 2. The device servos the output to maintain the ADJ pin voltage at 1.22V referenced to ground. The current in R1 is then equal to 1.22V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current. The ADJ pin bias current, 30nA at 25C, flows through R2 into the ADJ pin. The output voltage can be calculated using the formula in Figure 2. The value of R1 should be no greater than 250k to minimize errors in the output voltage caused by the ADJ pin bias current. Note that in shutdown the output is turned off and the divider current will be zero. Curves of ADJ Pin Voltage vs Temperature and ADJ Pin Bias Current vs Temperature appear in the Typical Performance Characteristics section. The adjustable device is tested and specified with the ADJ pin tied to the OUT pin for an output voltage of 1.22V. Specifications for output voltages greater than 1.22V will be proportional to the ratio of the desired output voltage to 1.22V: VOUT/1.22V. For example, load regulation for an output current change of 1mA to 150mA is -1mV typical at VOUT = 1.22V. At VOUT = 12V, load regulation is: (12V/1.22V)(-1mV) = - 9.8mV Bypass Capacitance and Low Noise Performance The LT1762 regulators may be used with the addition of a bypass capacitor from VOUT to the BYP pin to lower output voltage noise. A good quality low leakage capacitor is recommended. This capacitor will bypass the reference of the regulator, providing a low frequency noise pole. The noise pole provided by this bypass capacitor will lower the output voltage noise to as low as 20VRMS with the addition of a 0.01F bypass capacitor. Using a bypass capacitor has the added benefit of improving transient response. With no bypass capacitor and a 10F output capacitor, a 10mA to 150mA load step will settle to within 1% of its final value in less than 100s. With the addition of a 0.01F bypass capacitor, the output will stay within 1% for a 10mA to 150mA load step (see LT1762-5 Transient Response in the Typical Performance Characteristics). However, regulator start-up time is inversely proportional to the size of the bypass capacitor, slowing to 15ms with a 0.01F bypass capacitor and 10F output capacitor.
IN VIN
OUT
VOUT
+
LT1762 ADJ GND R1
1762 F02
R2
R2 VOUT = 1.22V 1 + + (IADJ )(R2) R1 VADJ = 1.22V IADJ = 30nA AT 25C OUTPUT RANGE = 1.22V TO 20V
Figure 2. Adjustable Operation
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LT1762 Series
APPLICATIONS INFORMATION
Output Capacitance and Transient Response The LT1762 regulators are designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 2.2F with an ESR of 3 or less is recommended to prevent oscillations. The LT1762-X is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT1762-X, will increase the effective output capacitor value. With larger capacitors used to bypass the reference (for low noise operation), larger values of output capacitors are needed. For 100pF of bypass capacitance, 3.3F of output capacitor is recommended. With a 330pF bypass capacitor or larger, a 4.7F output capacitor is recommended. The shaded region of Figure 3 defines the range over which the LT1762 regulators are stable. The minimum ESR needed is defined by the amount of bypass capacitance used, while the maximum ESR is 3. Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures 4 and 5. When used with a 5V regulator, a 10F Y5V capacitor can exhibit an effective value as low as 1F to 2F over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability
20 0
CHANGE IN VALUE (%)
4.0 3.5
3.0 STABLE REGION 2.5
ESR ()
2.0 1.5 1.0 0.5 0 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (F)
1762 F03
CHANGE IN VALUE (%)
CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP 3300pF
Figure 3. Stability
-80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F 50 25 75 0 TEMPERATURE (C) 100 125 -100 -50 -25
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BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F X5R
-20 -40 -60 Y5V -80
-100
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
14
16
1762 F04
Figure 4. Ceramic Capacitor DC Bias Characteristics
40 20 0 -20 -40 -60 Y5V X5R
1762 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
LT1762 Series
APPLICATIONS INFORMATION
across temperature, while the X5R is less expensive and is available in higher values. Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure 6's trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise. The GND pin current can be found by examining the GND Pin Current curves in the Typical Performance Characteristics. Power dissipation will be equal to the sum of the two components listed above. The LT1762 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions, the maximum junction temperature rating of 125C must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices. The following table lists thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with one ounce copper.
Table 1. Measured Thermal Resistance
COPPER AREA
100ms/DIV
1762 F05
LT1762-5 COUT = 10F CBYP = 0.01f ILOAD = 100mA VOUT 500V/DIV
Figure 6. Noise Resulting from Tapping on a Ceramic Capacitor
Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125C). The power dissipated by the device will be made up of two components: 1. Output current multiplied by the input/output voltage differential: (IOUT)(VIN - VOUT), and 2. GND pin current multiplied by the input voltage: (IGND)(VIN).
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THERMAL RESISTANCE BOARD AREA 2500mm 2500mm
2 2
TOPSIDE* 2500mm 1000mm
2 2
BACKSIDE 2500mm 2500mm
2 2
(JUNCTION-TO-AMBIENT) 110C/W 115C/W 120C/W 130C/W 140C/W
225mm2 100mm 50mm
2 2
2500mm2 2500mm 2500mm
2 2
2500mm2 2500mm 2500mm
2 2
*Device is mounted on topside.
Calculating Junction Temperature Example: Given an output voltage of 3.3V, an input voltage range of 4V to 6V, an output current range of 0mA to 50mA and a maximum ambient temperature of 50C, what will the maximum junction temperature be? The power dissipated by the device will be equal to: IOUT(MAX)(VIN(MAX) - VOUT) + IGND(VIN(MAX))
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LT1762 Series
APPLICATIONS INFORMATION
where, IOUT(MAX) = 150mA VIN(MAX) = 6V IGND at (IOUT = 150mA, VIN = 6V) = 5mA So, P = 150mA(6V - 3.3V) + 5mA(6V) = 0.44W The thermal resistance will be in the range of 110C/W to 140C/W depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: 0.44W(125C/W) = 55C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50C + 55C = 105C Protection Features The LT1762 regulators incorporate several protection features which make them ideal for use in battery-powered circuits. In addition to the normal protection features associated with monolithic regulators, such as current limiting and thermal limiting, the devices are protected against reverse input voltages, reverse output voltages and reverse voltages from output to input. Current limit protection and thermal overload protection are intended to protect the device against current overload conditions at the output of the device. For normal operation, the junction temperature should not exceed 125C. The input of the device will withstand reverse voltages of 20V. Current flow into the device will be limited to less than 1mA (typically less than 100A) and no negative voltage will appear at the output. The device will protect both itself and the load. This provides protection against batteries which can be plugged in backward. The output of the LT1762-X can be pulled below ground without damaging the device. If the input is left open circuit or grounded, the output can be pulled below ground by 20V. For fixed voltage versions, the output will act like a large resistor, typically 500k or higher, limiting current flow to less than 100A. For adjustable versions, the output will act like an open circuit; no current will flow out of the pin. If the input is powered by a voltage source, the output will source the short-circuit current of the device and will protect itself by thermal limiting. In this case, grounding the SHDN pin will turn off the device and stop the output from sourcing the short-circuit current. The ADJ pin of the adjustable device can be pulled above or below ground by as much as 7V without damaging the device. If the input is left open circuit or grounded, the ADJ pin will act like an open circuit when pulled below ground and like a large resistor (typically 100k) in series with a diode when pulled above ground. In situations where the ADJ pin is connected to a resistor divider that would pull the ADJ pin above its 7V clamp voltage if the output is pulled high, the ADJ pin input current must be limited to less than 5mA. For example, a resistor divider is used to provide a regulated 1.5V output from the 1.22V reference when the output is forced to 20V. The top resistor of the resistor divider must be chosen to limit the current into the ADJ pin to less than 5mA when the ADJ pin is at 7V. The 13V difference between output and ADJ pin divided by the 5mA maximum current into the ADJ pin yields a minimum top resistor value of 2.6k. In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left open circuit. Current flow back into the output will follow the curve shown in Figure 7. When the IN pin of the LT1762-X is forced below the OUT pin or the OUT pin is pulled above the IN pin, input current will typically drop to less than 2A. This can happen if the input of the device is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or a second regulator circuit. The state of the SHDN pin will have no effect on the reverse output current when the output is pulled above the input.
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LT1762 Series
APPLICATIONS INFORMATION
100
REVERSE OUTPUT CURRENT (A)
90 80 70 60 50 40 30 20 10 0 0
TJ = 25C VIN = 0V CURRENT FLOWS INTO OUTPUT PIN VOUT = VSENSE (LT1762-2.5/LT1762-3 LT1762-3.3/LT1762-5) VOUT = VADJ (LT1762) LT1762-3
1
Figure 7. Reverse Output Current
PACKAGE DESCRIPTION
MS8 Package 8-Lead Plastic MSOP
(LTC DWG # 05-08-1660)
0.007 (0.18) 0.021 0.006 (0.53 0.015)
* DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
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LT1762
LT1762-2.5
LT1762-5 LT1762-3.3 2 345678 OUTPUT VOLTAGE (V) 9 10
1762 F07
0.118 0.004* (3.00 0.102)
8
76
5
0.193 0.006 (4.90 0.15)
0.118 0.004** (3.00 0.102)
1 0.040 0.006 (1.02 0.15) 0 - 6 TYP SEATING PLANE 0.012 (0.30) 0.0256 REF (0.65) BSC
23
4 0.034 0.004 (0.86 0.102)
0.006 0.004 (0.15 0.102)
MSOP (MS8) 1098
15
LT1762 Series
TYPICAL APPLICATION
Paralleling of Regulators for Higher Output Current
R1 0.1
+
VIN > 3.7V
SHDN
RELATED PARTS
PART NUMBER LT1120 LT1121 LT1129 LT1175 LT1521 LT1529 LT1611 LT1613 LTC1627 LT1761 Series LT1763 Series DESCRIPTION 125mA Low Dropout Regulator with 20A IQ 150mA Micropower Low Dropout Regulator 700mA Micropower Low Dropout Regulator 500mA Negative Low Dropout Micropower Regulator 300mA Low Dropout Micropower Regulator with Shutdown 3A Low Dropout Regulator with 50A IQ Inverting 1.4MHz Switching Regulator 1.4MHz Single-Cell Micropower DC/DC Converter High Efficiency Synchronous Step-Down Switching Regulator 100mA, Low Noise, Low Dropout Micropower Regulators in SOT-23 500mA, Low Noise, LDO Micropower Regulators COMMENTS Includes 2.5V Reference and Comparator 30A IQ, SOT-223 Package 50A Quiescent Current 45A IQ, 0.26V Dropout Voltage, SOT-223 Package 15A IQ, Reverse Battery Protection 500mV Dropout Voltage 5V to - 5V at 150mA, Low Output Noise, SOT-23 Package SOT-23 Package, Internally Compensated Burst ModeTM Operation, Monolithic, 100% Duty Cycle 20A Quiescent Current, 20VRMS Noise 30A Quiescent Current, 20VRMS Noise
Burst Mode is a trademark of Linear Technology Corporation.
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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IN C1 10F
OUT FB LT1762-3.3 C4 0.01F
+
3.3V 300mA C2 10F
SHDN BYP GND R2 0.1 IN LT1762 BYP SHDN ADJ GND OUT C5 0.01F R6 2k
R7 1.21k
R3 2.2k
R4 2.2k
3
+ -
8 1
R5 10k
1/2 LT1490 2 4
1762 TA03
C3 0.01F
1762fs sn1762 LT/TP 0899 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1999

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