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LT1964 200mA, Low Noise, Low Dropout Negative Micropower Regulator FEATURES
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DESCRIPTION
The LT(R)1964 is a micropower low noise, low dropout negative regulator. The device is capable of supplying 200mA of output current with a dropout voltage of 340mV. Low quiescent current (30A operating and 3A shutdown) makes the LT1964 an excellent choice for battery-powered applications. Quiescent current is well controlled in dropout. Other features of the LT1964 include low output noise. With the addition of an external 0.01F bypass capacitor, output noise is reduced to 30VRMS over a 10Hz to 100kHz bandwidth. The LT1964 is capable of operating with small capacitors and is stable with output capacitors as low as 1F Small ceramic capacitors can be used without . the necessary addition of ESR as is common with other regulators. Internal protection circuitry includes reverse output protection, current limiting, and thermal limiting. The device is available with a fixed output voltage of -5V and as an adjustable device with a -1.22V reference voltage. The LT1964 regulators are available in a low profile (1mm) ThinSOT and the low profile (0.75mm) 8-pin (3mm x 3mm) DFN packages.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Low Noise: 30VRMS (10Hz to 100kHz) Low Quiescent Current: 30A Low Dropout Voltage: 340mV Output Current: 200mA Fixed Output Voltage: -5V Adjustable Output from -1.22V to - 20V Positive or Negative Shutdown Logic 3A Quiescent Current in Shutdown Stable with 1F Output Capacitor Stable with Aluminum, Tantalum, or Ceramic Capacitors Thermal Limiting Low Profile (1mm) ThinSOTTM and (0.75mm) 8-Pin 3mm x 3mm DFN Packages
APPLICATIONS
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Battery-Powered Instruments Low Noise Regulator for Noise-Sensitive Instrumentation Negative Complement to LT1761 Family of Positive LDOs
TYPICAL APPLICATION
10Hz to 100kHz Output Noise -5V Low Noise Regulator
1F VIN -5.4V TO -20V
GND SHDN BYP 0.01F
10F VOUT 100V/DIV 30VRMS
LT1964-5 IN OUT
-5V AT 200mA 30VRMS NOISE
1964 TA01a
1ms/DIV
1964 TA01b
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LT1964 ABSOLUTE MAXIMUM RATINGS
(Note 1)
IN Pin Voltage ........................................................ 20V OUT Pin Voltage (Note 11) ......................................20V OUT to IN Differential Voltage (Note 11) ........ -0.5V, 20V ADJ Pin Voltage (with Respect to IN Pin) (Note 11)............. -0.5V, 20V BYP Pin Voltage (with Respect to IN Pin)..................................... 20V SHDN Pin Voltage (with Respect to IN Pin) (Note 11)............. -0.5V, 35V
SHDN Pin Voltage (with Respect to GND Pin) ..........................-20V, 15V Output Short-Circuit Duration .......................... Indefinite Operating Junction Temperature (E, I Grade) Range (Note 10) ............................... - 40C to 125C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) SOT-23 Package................................................ 300C
PIN CONFIGURATION
LT1964 TOP VIEW TOP VIEW OUT OUT ADJ SHDN 1 2 3 4 9 8 IN 7 IN 6 GND 5 BYP S5 PACKAGE 5-LEAD PLASTIC SOT-23 TJMAX = 150C, JA 125C/W to 250C/W (NOTE 13) SEE THE APPLICATIONS INFORMATION SECTION GND 1 IN 2 SHDN 3 4 ADJ 5 OUT LT1964-SD
DD PACKAGE 8-LEAD (3mm 3mm) PLASTIC DFN TJMAX = 125C, JA = 40C/W, JC = 16C/W (NOTE 13) EXPOSED PAD (PIN 9) IS IN, MUST BE SOLDERED TO PCB LT1964-BYP TOP VIEW GND 1 IN 2 BYP 3 4 ADJ 5 OUT LT1964-5
TOP VIEW GND 1 IN 2 BYP 3 4 SHDN 5 OUT
S5 PACKAGE 5-LEAD PLASTIC SOT-23 TJMAX = 150C, JA 125C/W to 250C/W (NOTE 13) SEE THE APPLICATIONS INFORMATION SECTION
S5 PACKAGE 5-LEAD PLASTIC SOT-23 TJMAX = 150C, JA 125C/W to 250C/W (NOTE 13) SEE THE APPLICATIONS INFORMATION SECTION
ORDER INFORMATION
LEAD FREE FINISH LT1964ES5-SD#PBF LT1964ES5-BYP#PBF LT1964ES5-5#PBF LT1964EDD#PBF LT1964IS5-SD#PBF LT1964IS5-BYP#PBF LT1964IS5-5#PBF LT1964IDD#PBF TAPE AND REEL LT1964ES5-SD#TRPBF LT1964ES5-BYP#TRPBF LT1964ES5-5#TRPBF LT1964EDD#TRPBF LT1964IS5-SD#TRPBF LT1964IS5-BYP#TRPBF LT1964IS5-5#TRPBF LT1964IDD#TRPBF PART MARKING* LTVX LTVY LTVZ LDVM LTVX LTVY LTVZ LDVM PACKAGE DESCRIPTION 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 8-Lead (3mm x 3mm) Plastic DFN 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 8-Lead (3mm x 3mm) Plastic DFN TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C
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LT1964 ORDER INFORMATION
LEAD BASED FINISH LT1964ES5-SD LT1964ES5-BYP LT1964ES5-5 LT1964EDD LT1964IS5-SD LT1964IS5-BYP LT1964IS5-5 LT1964IDD TAPE AND REEL LT1964ES5-SD#TR LT1964ES5-BYP#TR LT1964ES5-5#TR LT1964EDD#TR LT1964IS5-SD#TR LT1964IS5-BYP#TR LT1964IS5-5#TR LT1964IDD#TR PART MARKING* LTVX LTVY LTVZ LDVM LTVX LTVY LTVZ LDVM PACKAGE DESCRIPTION 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 8-Lead (3mm x 3mm) Plastic DFN 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 5-Lead Plastic SOT-23 8-Lead (3mm x 3mm) Plastic DFN TEMPERATURE RANGE -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C -40C to 125C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
PARAMETER Regulated Output Voltage (Notes 3, 9) ADJ Pin Voltage (Notes 2, 3, 9) Line Regulation Load Regulation CONDITIONS LT1964-5 LT1964 LT1964-5 LT1964 (Note 2) LT1964-5 LT1964 Dropout Voltage VIN = VOUT(NOMINAL) (Notes 4, 5) ILOAD = -1mA ILOAD = -1mA ILOAD = -10mA ILOAD = -10mA ILOAD = -100mA ILOAD = -100mA ILOAD = -200mA ILOAD = -200mA GND Pin Current VIN = VOUT(NOMINAL) (Notes 4, 6) ILOAD = 0mA ILOAD = -1mA ILOAD = -10mA ILOAD = -100mA ILOAD = -200mA
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C.
MIN VIN = -5.5V, ILOAD = -1mA -20V < VIN < -6V, -200mA < ILOAD < -1mA VIN = -2V, ILOAD = -1mA -20V < VIN < -2.8V, -200mA < ILOAD < -1mA VIN = -5.5V to -20V, ILOAD = -1mA VIN = -2.8V to -20V, ILOAD = -1mA VIN = -6V, ILOAD = -1mA to -200mA VIN = -6V, ILOAD = -1mA to -200mA VIN = -2.8V, ILOAD = -1mA to -200mA VIN = -2.8V, ILOAD = -1mA to -200mA
l l l l l l l l l l l l l l l
TYP -5 -5 -1.22 -1.22 15 1 15 2 0.1 0.15 0.26 0.34 30 85 300 1.3 2.5
MAX -5.075 -5.150 -1.238 -1.256 50 12 35 50 7 15 0.15 0.19 0.20 0.25 0.33 0.39 0.42 0.49 70 180 600 3 6
UNITS V V V V mV mV mV mV mV mV V V V V V V V V A A A mA mA
-4.925 -4.850 -1.202 -1.184
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LT1964 ELECTRICAL CHARACTERISTICS
Output Voltage Noise ADJ Pin Bias Current Minimum Input Voltage (Note 12) ILOAD = -200mA Shutdown Threshold (Notes 2, 7) LT1964-BYP LT1964-SD VOUT = Off to On (Positive) VOUT = Off to On (Negative) VOUT = On to Off (Positive) VOUT = On to Off (Negative) VSHDN = 0V VSHDN = 15V VSHDN = -15V VIN = -6V, VSHDN = 0V VIN - VOUT = -1.5V(Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = -200mA VIN = -6V, VOUT = 0V VIN = VOUT(NOMINAL) -1.5V, VOUT = 0.1V VIN = 20V, VOUT, VADJ, VSHDN = Open Circuit
l l l l l l l l l
The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C.
COUT = 10F CBYP = 0.01F ILOAD = -200mA, BW = 10Hz to 100kHz , , 30 30 -1.9 -1.6 1.6 -1.9 0.8 -0.8 0.1 6 -3 3 46 54 350 220 1 100 -2.8 -2.2 2.1 -2.8 VRMS nA V V V V V V A A A A dB mA mA mA
0.25 -0.25 -1
SHDN Pin Current (Note 8)
1 15 -9 10
Quiescent Current in Shutdown Ripple Rejection Current Limit Input Reverse Leakage Current
Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime Note 2: The LT1964 (adjustable version) is tested and specified for these conditions with the ADJ pin connected to the OUT pin. Note 3: 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 4: To satisfy requirements for minimum input voltage, the LT1964 (adjustable version) is tested and specified for these conditions with an external resistor divider (two 249k resistors) for an output voltage of -2.44V. The external resistor divider will add a 5A DC load on the output. Note 5: 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 6: 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 7: ADJ pin bias current flows out of the ADJ pin. Note 8: Positive SHDN pin current flows into the SHDN pin. SHDN pin current is included in the GND pin current specification. Note 9: For input-to-output differential voltages greater than 7V, a 50A load is needed to maintain regulation. Note 10: The LT1964 is tested and specified under pulse load conditions such that TJ TA. The LT1964E is tested at TA = 25C. Performance at -40C to 125C is assured by design, characterization and correlation with statistical process controls. The LT1964I is guaranteed over the full -40C to 125C operating junction temperature range. Note 11: A parasitic diode exists internally on the LT1964 between the OUT, ADJ and SHDN pins and the IN pin. The OUT, ADJ and SHDN pins cannot be pulled more than 0.5V more negative than the IN pin during fault conditions, and must remain at a voltage more positive than the IN pin during operation. Note 12: For the LT1964-BYP this specification accounts for the operating , threshold of the SHDN pin, which is tied to the IN pin internally. For the LT1964-SD, the SHDN threshold must be met to ensure device operation. Note 13: Actual thermal resistance (JA) junction to ambient will be a function of board layout. See the Thermal Considerations section in the Applications Information.
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LT1964 TYPICAL PERFORMANCE CHARACTERISTICS
Typical Dropout Voltage
500 450 DROPOUT VOLTAGE (mV) DROPOUT VOLTAGE (mV) 400 350 300 250 200 150 100 50 0 0 -40 -80 -120 -160 OUTPUT CURRENT (mA) -200
1964 G01
Guaranteed Dropout Voltage
500 450 DROPOUT VOLTAGE (mV) = TEST POINT 500 450 TJ 125C 400 350 300 250 200 150 100 50 0 -40 -80 -120 -160 OUTPUT CURRENT (mA) -200
1964 G02
Dropout Voltage
TJ = 125C
400 350 300 250 200 150 100 50 0
IL = -200mA IL = -100mA IL = -50mA IL = -10mA IL = -1mA
TJ = 25C
TJ 25C
0 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
1964 G03
Quiescent Current
-50 -45 QUIESCENT CURRENT (A) -40 -35 -30 -25 -20 -15 -10 -5 0 -50 -25 VSHDN = 0V 0 25 50 75 TEMPERATURE (C) 100 125 VSHDN = VIN VIN = -6V RL = 250k ( FOR LT1964-5) IL = -5A (0 FOR LT1964-5) OUTPUT VOLTAGE (V) -5.12 -5.09 -5.06 -5.03 -5.00 -4.97 -4.94 -4.91
LT1964-5 Output Voltage
-1.240 IL = -1mA -1.235 ADJ PIN VOLTAGE (V) -1.230 -1.225 -1.220 -1.215 -1.210 -1.205 -25 0 25 50 75 TEMPERATURE (C) 100 125
LT1964 ADJ Pin Voltage
IL = -1mA
-4.88 -50
-1.200 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
1964 G05 1964 G04
1964 G06
LT1964-5 Quiescent Current
-40 -35 QUIESCENT CURRENT (A) -30 -25 -20 -15 -10 -5 -0 0 VSHDN = 0V TJ = 25C RL = VSHDN = VIN -40 -35 QUIESCENT CURRENT (A) -30 -25 -20 -15 -10 -5 -0
LT1964 Quiescent Current
-3.0 TJ = 25C RL = 250k IL = -5A VSHDN = VIN GND PIN CURRENT (mA) -2.5 -2.0 -1.5 -1.0 -0.5 0
LT1964-5 GND Pin Current
TJ = 25C VSHDN = VIN *FOR VOUT = -5V RL = 25 IL = -200mA*
RL = 50 IL = -100mA* RL = 100 IL = -50mA* RL = 500 IL = -10mA* 0 -1 -2 -3 -4 -5 -6 -7 -8 -9 -10 INPUT VOLTAGE (V)
1964 G09
VSHDN = 0V
-1 -2 -3 -4 -5 -6 -7 -8 -9 -10 INPUT VOLTAGE (V)
1964 G07
0
-1 -2 -3 -4 -5 -6 -7 -8 -9 -10 INPUT VOLTAGE (V)
1964 G08
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LT1964 TYPICAL PERFORMANCE CHARACTERISTICS
LT1964 GND Pin Current
-3.0 -2.5 GND PIN CURRENT (mA) -2.0 -1.5 -1.0 -0.5 0 RL = 12.2 IL = -100mA* RL = 24.4 IL = -50mA* RL = 122 IL = -10mA* TJ = 25C; VSHDN = VIN; *FOR VOUT = -1.22V RL = 6.1 IL = -200mA* -4.0 -3.5 GND PIN CURRENT (mA) SHDN PIN VOLTAGE (V) -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0 0 -40 -80 -120 -160 OUTPUT CURRENT (mA) -200
1964 G11
GND Pin Current vs ILOAD
VIN = VOUT(NOMINAL) - 1V TJ = -50C 2.5 2.0 1.5 1.0 0.5 0 -0.5 -1.0 -1.5 -2.0
SHDN Pin Thresholds
ON
TJ = 25C TJ = 125C
OFF
ON
0
-1 -2 -3 -4 -5 -6 -7 -8 -9 -10 INPUT VOLTAGE (V)
1964 G10
-2.5 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
1964 G12
SHDN Pin Input Current
10 8 SHDN PIN INPUT CURRENT (A) 6 4 2 0 -2 -4 -6 -8 -10 -10 -8 -6 -4 -2 0 2 4 6 SHDN PIN VOLTAGE (V) 8 10 SHDN PIN INPUT CURRENT (A) TJ = 25C POSITIVE CURRENT FLOWS INTO THE PIN 12 9 6
SHDN Pin Input Current
-70 VIN = -15V POSITIVE CURRENT FLOWS INTO THE PIN VSHDN = 15V 3 0 -3 -6 -9 -50 VSHDN = -15V -60 ADJ PIN BIAS CURRENT (nA) -50 -40 -30 -20 -10
ADJ Pin Bias Current
-25
0 25 50 75 TEMPERATURE (C)
100
125
0 -50
-25
0 25 50 75 TEMPERATURE (C)
100
125
1964 G13
1964 G14
1964 G15
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LT1964 TYPICAL PERFORMANCE CHARACTERISTICS
Current Limit
-600 VOUT = 100mV -500 CURRENT LIMIT (mA) -400 -300 -200 -100 0 CURRENT LIMIT (mA) -500 -400 -300 -200 -100 0 -50 -600 VIN = -7V VOUT = 0V RIPPLE REJECTION (dB)
Current Limit
80 70 60 50 40 30 20 10 -25 0 25 50 75 TEMPERATURE (C) 100 125 0
Input Ripple Rejection
IL = -200mA VIN = VOUT(NOMINAL) - 1V + 50mVRMS RIPPLE CBYP = 0
COUT = 10F
COUT = 1F 10 100 1k 10k FREQUENCY (Hz) 100k 1M
1964 G18
0
-4 -8 -12 -16 INPUT/OUTPUT DIFFERENTIAL (V)
-20
1964 G16
1964 G17
Input Ripple Rejection
60 58 RIPPLE REJECTION (dB) 56 54 52 50 48 46 44 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 VIN = VOUT(NOMINAL) - 1V + 0.5VP-P RIPPLE AT f = 120Hz IL = -200mA -3.0 -2.5 -2.0
LT1964-BYP Minimum Input Voltage
-3.0 -2.5 -2.0
LT1964, LT1964-SD Minimum Input Voltage
MINIMUM INPUT VOLTAGE (V)
IL = -200mA -1.5 IL = -1mA -1.0 -0.5 0 -50 NOTE: THE MINIMUM INPUT VOLTAGE ACCOUNTS FOR THE OPERATING THRESHOLD OF THE SHDN PIN WHICH IS TIED TO THE IN PIN INTERNALLY -25 0 25 50 75 TEMPERATURE (C) 100 125
MINIMUM INPUT VOLTAGE (V)
IL = -200mA -1.5 -1.0 -0.5 0 -50 IL = -1mA NOTE: THE SHDN PIN THRESHOLD MUST BE MET TO ENSURE DEVICE OPERATION -25 0 25 50 75 TEMPERATURE (C) 100 125
1964 G19
1964 G20
1964 G21
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LT1964 TYPICAL PERFORMANCE CHARACTERISTICS
Load Regulation
OUTPUT NOISE SPECTRAL DENSITY (V/Hz) 30 IL = -1mA TO -200mA 25 LOAD REGULATION (mV) 20 15 10 5 0 -50 10 CBYP = 1000pF CBYP = 100pF OUTPUT NOISE (VRMS) 1 CBYP = 0
Output Noise Spectral Density
140 120
RMS Output Noise vs Bypass Capacitor
COUT = 10F IL = -200mA f = 10Hz TO 100kHz
LT1964-5 100 80 60 40 LT1964 20 0
LT1964-5
0.1
CBYP = 0.01F COUT = 10F IL = 200mA LT1964-5 LT1964 1k 10k FREQUENCY (Hz) 100k
1964 G23
LT1964 -25 0 25 50 75 TEMPERATURE (C) 100 125
0.01 10 100
10
100 CBYP (pF)
1k
10k
1964 G24
1964 G22
RMS Output Noise vs Load Current
140 COUT = 10F 120 OUTPUT NOISE (VRMS) 100 80 CBYP = 0 60 40 20 0 -0.01 LT1964-5 LT1964 CBYP = 0.01F -0.1 -1 -10 -100 LOAD CURRENT (mA) -1k
1964 G25
LT1964-5, 10Hz to 100kHz Output Noise, CBYP = 0
LT1964-5, 10Hz to 100kHz Output Noise, CBYP = 100pF
LT1964-5
VOUT 200V/DIV LT1964
VOUT 100V/DIV
COUT = 10F ILOAD = -200mA
1ms/DIV
1964 G26
COUT = 10F ILOAD = -200mA
1ms/DIV
1964 G27
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LT1964
LT1964-5, 10Hz to 100kHz Output Noise, CBYP = 1000pF
LT1964-5, 10Hz to 100kHz Output Noise, CBYP = 0.01F
VOUT 100V/DIV
VOUT 100V/DIV
COUT = 10F ILOAD = -200mA
1ms/DIV
1964 G28
COUT = 10F ILOAD = -200mA
1ms/DIV
1964 G29
LT1964-5, Transient Response, CBYP = 0
OUTPUT VOLTAGE DEVIATION (V) OUTPUT VOLTAGE DEVIATION (V) 0.2 0.1 0 -0.1 -0.2 VIN = -6V CIN = 10F COUT = 10F 0.04 0.02 0 -0.02 -0.04
LT1964-5, Transient Response, CBYP = 0.01F
VIN = -6V CIN = 10F COUT = 10F
LOAD CURRENT (mA)
0 -100 -200 0 400 800 1200 TIME (s) 1600 2000
1964 G30
LOAD CURRENT (mA)
0 -100 -200 0 20 40 60 80 100 120 140 160 180 200 TIME (s)
1964 G31
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LT1964 PIN FUNCTIONS
ADJ (Adjustable Devices only): For the Adjustable LT1964, this is the Input to the Error Amplifier. The ADJ pin has a bias current of 30nA that flows out of the pin. The ADJ pin voltage is -1.22V referenced to ground, and the output voltage range is -1.22V to -20V. A parasitic diode exists between the ADJ pin and the input of the LT1964. The ADJ pin cannot be pulled more negative than the input during normal operation, or more than 0.5V more negative than the input during a fault condition. BYP: The BYP Pin is used to Bypass the Reference of the LT1964 to Achieve Low Noise Performance from the Regulator. 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 30VRMS over a 10Hz to 100kHz bandwidth. If not used, this pin must be left unconnected. Exposed Pad (DFN Package Only): IN. Connect to IN (Pins 7, 8) at the PCB. GND: Ground. IN: Power is Supplied to the Device Through the Input 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. OUT: The Output Supplies Power to the Load. A minimum output capacitor of 1F is required to prevent oscillations. Larger output capacitors will be required for applications with large transient loads to limit peak voltage transients. A parasitic diode exists between the output and the input. The output cannot be pulled more negative than the input during normal operation, or more than 0.5V below the input during a fault condition. See the Applications Information section for more information on output capacitance and reverse output characteristics. SHDN: The SHDN Pin is used to put the LT1964 into a Low Power Shutdown State. The SHDN pin is referenced to the GND pin for regulator control, allowing the LT1964 to be driven by either positive or negative logic. The output of the LT1964 will be off when the SHDN pin is pulled within 0.8V of GND. Pulling the SHDN pin more than -1.9V or +1.6V will turn the LT1964 on. The SHDN pin can be driven by 5V logic or open collector logic with a pull-up resistor. The pull-up resistor is required to supply the pull-up current of the open collector gate, normally several microamperes, and the SHDN pin current, typically 3A out of the pin (for negative logic) or 6A into the pin (for positive logic). If unused, the SHDN pin must be connected to VIN. The device will be shut down if the SHDN pin is open circuit. For the LT1964-BYP the SHDN , pin is internally connected to VIN. A parasitic diode exists between the SHDN pin and the input of the LT1964. The SHDN pin cannot be pulled more negative than the input during normal operation, or more than 0.5V below the input during a fault condition.
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LT1964 APPLICATIONS INFORMATION
The LT1964 is a 200mA negative low dropout regulator with micropower quiescent current and shutdown. The device is capable of supplying 200mA at a dropout voltage of 340mV. Output voltage noise can be lowered to 30VRMS 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 (30A) drops to 3A in shutdown. In addition to the low quiescent current, the LT1964 incorporates several protection features which make it ideal for use in battery-powered systems. In dual supply applications where the regulator load is returned to a positive supply, the output can be pulled above ground by as much as 20V and still allow the device to start and operate. Adjustable Operation The adjustable version of the LT1964 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 1. The device servos the output to maintain the voltage at the ADJ pin 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 out of the ADJ pin. The output voltage can be calculated using Bypass Capacitance and Low Noise Performance The LT1964 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 LT1964, providing a low frequency noise pole. The noise pole provided by this bypass capacitor will lower the output voltage noise to as low as 30VRMS 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 -200mA 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 the same -10mA to -200mA load step (see LT1964-5 Transient Response in the Typical Characteristics section). However, regulator start-up time is proportional to the size of the bypass capacitor. Higher values of output voltage noise may be measured if care is not exercised with regard to circuit layout and testing. Crosstalk from nearby traces can induce unwanted noise onto the output of the LT1964-X. the formula in Figure 1. The value of R1 should be less 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 and a 5A DC load (unless otherwise specified) 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 200mA is 2mV typical at VOUT = -1.22V. At VOUT = -12V, load regulation is: (-12V/-1.22V) * (2mV) = 19.6mV
R1 GND VIN ADJ LT1964 IN OUT R2
+
VOUT
1964 F01
VOUT = -1.22V(1 + R2 ) - (IADJ)(R2) R1 VADJ = -1.22V IADJ = 30nA AT 25C OUTPUT RANGE = -1.22V TO -20V
Figure 1. Adjustable Operation
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LT1964 APPLICATIONS INFORMATION
Output Capacitance and Transient Response The LT1964 is 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 1F with an ESR of 3 or less is recommended to prevent oscillations. The LT1964 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 LT1964, will increase the effective output capacitor value. 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 specified with EIA temperature characteristic codes of Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but they tend to have strong voltage and temperature coefficients as shown in Figures 2 and 3. When used with a 5V regulator, a 16V 10F Y5V capacitor can exhibit an effective value as low as 1F to 2F for the DC bias voltage applied and 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 across temperature, while the X5R is less expensive and is available in higher values. Care still must be exercised when using X5R and X7R capacitors; the X5R and X7R codes only specify operating temperature range and maximum capacitance change over temperature. Capacitance change due to DC bias with X5R and X7R capacitors is better than Y5V and Z5U capacitors, but can still be significant enough to drop capacitor values below appropriate levels. Capacitor DC bias characteristics tend to improve as component case size increases, but expected capacitance at operating voltage should be verified. 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
20 0 CHANGE IN VALUE (%) X5R -20 -40 -60 Y5V -80 -100 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
14
16
1964 F02
Figure 2. Ceramic Capacitor DC Bias Characteristics
40 20 CHANGE IN VALUE (%) 0 -20 -40 -60 -80 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F 50 25 75 0 TEMPERATURE (C) 100 125 Y5V X5R
-100 -50 -25
1964 F03
Figure 3. Ceramic Capacitor Temperature Characteristics
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12
LT1964 APPLICATIONS INFORMATION
amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure 4's trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise. 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 tables list 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.
VOUT 1mV/DIV
Table 1. SOT-23 Thermal Resistance
COPPER AREA TOPSIDE* 2500mm2
LT1964-5 COUT = 10F CBYP = 0.01F ILOAD = -200mA 100ms/DIV
1964 F04
BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 2500mm2
BOARD AREA 2500mm2 2500mm2 2500mm2 2500mm2 2500mm2
THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 125C/W 125C/W 130C/W 135C/W 150C/W
1000mm2 225mm2 100mm2 50mm2
Figure 4. Noise Resulting from Tapping on a Ceramic Capacitor
*Device is mounted on topside.
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. Ground pin current multiplied by the input voltage: IGND * VIN 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 LT1964 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.
Table 2. DFN Thermal Resistance
COPPER AREA TOPSIDE* 2500mm2 1000mm2 225mm2 100mm2 BACKSIDE 2500mm2 2500mm2 2500mm2 2500mm2 BOARD AREA 2500mm2 2500mm2 2500mm2 2500mm2 THERMAL RESISTANCE (JUNCTION-TO-AMBIENT) 40C/W 45C/W 50C/W 62C/W
*Device is mounted on topside.
The thermal resistance junction-to-case (JC), measured at Pin 2, is 60C/W. for the SOT-23 package and is 16C/W measured at the backside of the exposed pad on the DFN package Calculating Junction Temperature Example: Given an output voltage of -5V, an input voltage range of -6V to -8V, an output current range of 0mA to -100mA, and a maximum ambient temperature of 50C, what will the maximum junction temperature be? The power dissipated by the device will be equal to:
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LT1964 APPLICATIONS INFORMATION
IOUT(MAX) * (VIN(MAX) - VOUT) + (IGND * VIN(MAX)) where, IOUT(MAX) = -100mA VIN(MAX) = -8V IGND at (IOUT = -100mA, VIN = -8V) = -2mA so, P = -100mA * (-8V + 5V) + (-2mA * -8V) = 0.32W The thermal resistance (junction to ambient) will be in the range of 125C/W to 150C/W for the SOT-23 package depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: 0.32W * 140C/W = 44.2C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50C + 44.2C = 94.2C Protection Features The LT1964 incorporates several protection features which make it 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 device is protected against reverse input voltages and reverse output voltages. 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 output of the LT1964 can be pulled above ground without damaging the device. If the input is left open circuit or grounded, the output can be pulled above 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 40A. For adjustable versions, the output will act like an open circuit, no current will flow into the pin. If the input is powered by a voltage source, the output will sink 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 sinking the short-circuit current. Like many IC power regulators, the LT1964 series have safe operating area protection. The safe area protection activates at input-to-output differential voltages greater than -7V. The safe area protection decreases the current limit as the input-to-output differential voltage increases and keeps the power transistor inside a safe operating region for all values of forward input to-output voltage. The protection is designed to provide some output current at all values of input-to-output voltage up to the device breakdown. A 50A load is required at input-to-output differential voltages greater than -7V. When power is first turned on, as the input voltage rises, the output follows the input, allowing the regulator to start up into very heavy loads. During start-up, as the input voltage is rising, the input-to-output voltage differential is small, allowing the regulator to supply large output currents. With a high input voltage, a problem can occur wherein removal of an output short will not allow the output voltage to fully recover. Other regulators, such as the LT1175, also exhibit this phenomenon, so it is not unique to the LT1964 series. The problem occurs with a heavy output load when the input voltage is high and the output voltage is low. Common situations are immediately after the removal of a short-circuit or when the SHDN pin is pulled high after the input voltage has already been turned on. The load line for such a load may intersect the output current curve at two points. If this happens, there are two stable operating points for the regulator. With this double intersection, the input supply may need to be cycled down to zero and brought up again to make the output recover.
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14
LT1964 PACKAGE DESCRIPTION
S5 Package 5-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1635)
0.62 MAX 0.95 REF 2.90 BSC (NOTE 4)
1.22 REF
3.85 MAX 2.62 REF
1.4 MIN
2.80 BSC
1.50 - 1.75 (NOTE 4)
PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 - 0.45 TYP 5 PLCS (NOTE 3)
0.95 BSC
0.80 - 0.90 0.20 BSC 1.00 MAX DATUM `A' 0.01 - 0.10
0.30 - 0.50 REF 0.09 - 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193
1.90 BSC
S5 TSOT-23 0302 REV B
DD Package 8-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1698)
R = 0.115 TYP 5 0.675 0.05 0.38 0.10 8
3.5 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS PIN 1 TOP MARK (NOTE 6)
3.00 0.10 (4 SIDES)
1.65 0.10 (2 SIDES)
(DD) DFN 1203
0.200 REF
0.75 0.05
4 0.25 0.05 2.38 0.10 (2 SIDES)
1 0.50 BSC
0.00 - 0.05
BOTTOM VIEW--EXPOSED PAD NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON TOP AND BOTTOM OF PACKAGE
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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.
15
LT1964 RELATED PARTS
PART NUMBER LT1120 LT1121 LT1129 LT1175 LT1611 LT1761 Series LT1762 Series LT1763 Series LT1764A LT1931/LT1931A LT1962 LT1963A DESCRIPTION 125mA Micropower Low Dropout Regulator with Comparator and Shutdown 150mA Micropower Low Dropout Regulator 700mA Micropower Low Dropout Regulator 800mA Negative Low Dropout Micropower Regulator Inverting 1.4MHz Switching Regulator 100mA, Low Noise, Low Dropout Micropower Regulators 150mA, Low Noise, LDO Micropower Regulators 500mA, Low Noise, LDO Micropower Regulators 3A, Low Noise, Fast Transient Response LDO Inverting 1.2MHz/2.2MHz Switching Regulators 300mA, Low Noise, LDO Micropower Regulator 1.5A, Low Noise, Fast Transient Response LDO COMMENTS Includes 2.5V Reference and Comparator, VIN: 3.5V to 36V, IQ = 40A, N8 Package VIN: 4.2V to 30V, IQ = 30A; ThinSOT, S8 and MS8 Packages VIN: 4.5V to 30V, IQ = 50A; DD and S8 Packages VIN: 4.5V to 20V, IQ = 45A, 0.26V Dropout Voltage, S8 and ThinSOT Packages -5V at 150mA from 5V Input, ThinSOT Package VIN: 1.5V to 20V, IQ = 20A, 20VRMS Noise, ThinSOT Package VIN: 1.5V to 20V, IQ = 25A, 20VRMS Noise, MS8 Package VIN: 1.5V to 20V, IQ = 30A, 20VRMS Noise, S8 Package VIN: 1.5V to 20V, 40VRMS Noise; DD and T5 Packages -5V at 350mA from 5V Input, ThinSOT Package VIN: 1.5V to 20V, IQ = 30A, 20VRMS Noise, MS8 Package VIN: 1.5V to 20V, 40VRMS Noise; DD, T5, S8 and ThinSOT Packages
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16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0708 REV B * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2001

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