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LT1460S3-2.5 (SOT-23) Micropower Series Reference in SOT-23
FEATURES
s s s s s s s s
DESCRIPTION
The LT (R)1460S3-2.5 is a SOT-23 micropower series reference that combines high accuracy and low drift with low power dissipation and small package size. This series reference uses curvature compensation to obtain low temperature coefficient, and laser trimmed precision thin-film resistors to achieve high output accuracy. Furthermore, output shift due to PC board soldering stress has been dramatically reduced. The reference will supply up to 20mA, making it ideal for precision regulator applications, yet it is almost totally immune to input voltage variations. This series reference provides supply current and power dissipation advantages over shunt references that must idle the entire load current to operate. Additionally, the LT1460S32.5 does not require an output compensation capacitor, but is stable with any capacitive load. This feature is important in critical applications where PC board space is a premium or fast settling is demanded. Reverse-battery protection keeps the reference from conducting current. For even tighter tolerance and lower temperature coefficient, the LT1460 is also available in the 8-lead MSOP, SO, PDIP and the 3-lead TO-92 packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
3-Lead SOT-23 Package Low Drift: 20ppm/C Max High Accuracy: 0.2% Max Low Supply Current: 130A Max 20mA Output Current Guaranteed Stable with Any Capacitive Load Reverse-Battery Protection Low PC Board Solder Stress: 0.02% Typ
APPLICATIONS
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Handheld Instruments Precision Regulators A/D and D/A Converters Power Supplies Hard Disk Drives
TYPICAL APPLICATION
Typical Distribution of SOT-23 LT1460HC VOUT After IR Reflow Solder per JEDEC JESD22-A112
48 44 40 36 DISTRIBUTION (%) 32 28 24 20 16 12 8 4 0 2.490 2.500 OUTPUT VOLTAGE (V) 2.510
1460S3 TA02
Basic Connection
3.4V TO 20V C1 0.1F LT1460S3-2.5 IN GND
1460S3 TA01
OUT
2.5V
U
U
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LT1460HC LIMITS
1
LT1460S3-2.5 (SOT-23)
ABSOLUTE MAXIMUM RATINGS
Input Voltage ........................................................... 30V Reverse Voltage .................................................... - 15V Output Short-Circuit Duration, TA = 25C VIN > 10V ........................................................... 5 sec VIN 10V ................................................... Indefinite Specified Temperature Range ..................... 0C to 70C Storage Temperature Range (Note 1) ... - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
PACKAGE/ORDER INFORMATION
ORDER PART NUMBER
TOP VIEW IN 1 3 GND OUT 2 S3 PACKAGE 3-LEAD PLASTIC SOT-23
TJMAX = 125C, JA = 325C/ W
LT1460HCS3-2.5 LT1460JCS3-2.5 LT1460KCS3-2.5 S3 PART MARKING LTAC LTAD LTAE
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER Output Voltage (Note 2)
VIN = VOUT + 2.5V, IOUT = 0, TA = 25C unless otherwise specified.
MIN 2.495 - 0.2 2.490 - 0.4 2.4875 - 0.5
q q q q
CONDITIONS LT1460HCS3 LT1460JCS3 LT1460KCS3
TYP 2.500 2.500 2.500
MAX 2.505 0.2 2.510 0.4 2.5125 0.5 20 20 50 800 1000 100 130 6000 8000 400 500 300 380 10 0.9 1.3 1.4
UNITS V % V % V % ppm/C ppm/C ppm/C ppm/V ppm/V ppm/V ppm/V ppm/mA ppm/mA ppm/mA ppm/mA ppm/mA ppm/mA ppm/mW V V V mA A
Output Voltage Temperature Coefficient (Note 3)
TMIN TJ TMAX LT1460HCS3 LT1460JCS3 LT1460KCS3 3.4V VIN 5V 5V VIN 20V
10 10 25 150 50
Line Regulation
q
Load Regulation Sourcing (Note 4)
IOUT = 100A
q
4300 280
q
IOUT = 10mA IOUT = 20mA 0C TA 70C Thermal Regulation (Note 5) Dropout Voltage (Note 6) P = 200mW VIN - VOUT, VOUT 0.2%, IOUT = 0 VIN - VOUT, VOUT 0.2%, IOUT = 10mA
q q
220
q
2.5
Output Current Reverse Leakage
Short VOUT to GND VIN = - 15V
q
40 0.5 10
2
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W
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LT1460S3-2.5 (SOT-23)
ELECTRICAL CHARACTERISTICS
PARAMETER Supply Current
VIN = VOUT + 2.5V, IOUT = 0, TA = 25C unless otherwise specified.
MIN
q
CONDITIONS
TYP 100
MAX 130 165
UNITS A A VP-P VRMS ppm/kHr ppm
Output Voltage Noise (Note 7) Long-Term Stability of Output Voltage (Note 8) Hysteresis (Note 9)
0.1Hz f 10Hz 10Hz f 1kHz T = 0C to 70C
10 10 70 100
The q denotes specifications which apply over the full specified temperature range. Note 1: If the part is stored outside of the specified temperature range, the output may shift due to hysteresis. Note 2: ESD (Electrostatic Discharge) sensitive device. Extensive use of ESD protection devices are used internal to the LT1460S3-2.5, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. Note 3: Temperature coefficient is measured by dividing the change in output voltage by the specified temperature range. Incremental slope is also measured at 25C. Note 4: Load regulation is measured on a pulse basis from no load to the specified load current. Output changes due to die temperature change must be taken into account separately. Note 5: Thermal regulation is caused by die temperature gradients created by load current or input voltage changes. This effect must be added to normal line or load regulation. This parameter is not 100% tested. Note 6: Excludes load regulation errors. Note 7: Peak-to-peak noise is measured with a single highpass filter at 0.1Hz and 2-pole lowpass filter at 10Hz. The unit is enclosed in a still-air environment to eliminate thermocouple effects on the leads. The test time
is 10 sec. RMS noise is measured with a single highpass filter at 10Hz and a 2-pole lowpass filter at 1kHz. The resulting output is full wave rectified and then integrated for a fixed period, making the final reading an average as opposed to RMS. A correction factor of 1.1 is used to convert from average to RMS and a second correction of 0.88 is used to correct for the nonideal bandpass of the filters. Note 8: Long-term stability typically has a logarithmic characteristic and therefore, changes after 1000 hours tend to be much smaller than before that time. Total drift in the second thousand hours is normally less than one third that of the first thousand hours with a continuing trend toward reduced drift with time. Significant improvement in long-term drift can be realized by preconditioning the IC with a 100 hour to 200 hour, 125C burn-in. Long-term stability will also be effected by differential stresses between the IC and the board material created during board assembly. Note 9: Hysteresis in output voltage is created by package stress that differs depending on whether the IC was previously at a higher or lower temperature. Output voltage is always measured at 25C, but the IC is cycled to 70C or 0C before successive measurements. Hysteresis is roughly proportional to the square of the temperature change. Hysteresis is not normally a problem for operational temperature excursions where the instrument might be stored at high or low temperature.
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Input-Output Voltage Differential
100
OUTPUT VOLTAGE CHANGE (mV)
OUTPUT VOLTAGE CHANGE (mV)
OUTPUT CURRENT (mA)
10
-55C 1 125C 25C
0.1 0 0.5 1.0 1.5 2.0 INPUT-OUTPUT VOLTAGE (V) 2.5
UW
1460S3 G01
Load Regulation, Sourcing
20 18 16 14 12 10 25C 8 6 4 2 0 0.1 1 10 OUTPUT CURRENT (mA) 100
1460S3 G02
Load Regulation, Sinking
60 50 125C 40 30 25C 20 - 55C 10 0 0 0.25 0.50 0.75 OUTPUT CURRENT (mA) 1
1460S3 G03
125C
- 55C
3
LT1460S3-2.5 (SOT-23) TYPICAL PERFORMANCE CHARACTERISTICS
Output Voltage Temperature Drift
2.504 2.503
175 150 125C
SUPPLY CURRENT (A)
OUTPUT VOLTAGE (V)
125 100 75 50 25 0
2.501 2.500 2.499 2.498 3 TYPICAL PARTS 2.497 2.496 - 50 - 25 50 25 TEMPERATURE (C) 0 75 100
25C
OUTPUT VOLTGAE (V)
2.502
Power Supply Rejection Ratio vs Frequency
100
1000
POWER SUPPLY REJECTION RATIO (dB)
90 80 70 60 50 40 30 20 10 0 0.1 1 10 100 FREQUENCY (kHz) 1000
1460S3 G07
OUTPUT IMPEDANCE ()
CL = 0 100 CL = 0.1F
LOAD CAPACITANCE (F)
Output Voltage Noise Spectrum
1000
OUTPUT NOISE (10V/DIV)
NOISE VOLTAGE (nV/Hz)
OUTPUT VOLTAGE (V)
100 0.01
0.1
1 10 FREQUENCY (kHz)
4
UW
1460S3 G10
Supply Current vs Input Voltage
2.504 2.503 2.502
Line Regulation
125C
25C 2.501 2.500 - 55C 2.499 2.498
-55C
0
5
10 INPUT VOLTAGE (V)
15
20
1460S3 G05
0
2
4
6 8 10 12 14 16 18 20 INPUT VOLTAGE (V)
1460S3 G06
1460S3 G04
Output Impedance vs Frequency
10
Transient Response
1
0.1
10 CL = 1F
0 IOUT = 10mA
1460S3 G09
1 0.01
0.1
1 10 FREQUENCY (kHz)
100
1000
1460S3 G08
Output Noise 0.1Hz to 10Hz
2.5052
Long-Term Drift-- Three Typical Parts
2.5050
2.5048
2.5046
2.5044
2.5042
100
0
1
2
3
456 TIME (SEC)
7
8
9
10
0
200
600 400 TIME (HOURS)
800
1000
1460S3 G12
1460S3 G11
LT1460S3-2.5 (SOT-23)
APPLICATIONS INFORMATION
Longer Battery Life Series references have a large advantage over older shunt style references. Shunt references require a resistor from the power supply to operate. This resistor must be chosen to supply the maximum current that can ever be demanded by the circuit being regulated. When the circuit being controlled is not operating at this maximum current, the shunt reference must always sink this current, resulting in high dissipation and short battery life. The LT1460S3-2.5 series reference does not require a current setting resistor and can operate with any supply voltage from VOUT + 0.9V to 20V. When the circuitry being regulated does not demand current, the LT1460S3-2.5 reduces its dissipation and battery life is extended. If the reference is not delivering load current it dissipates only 500W on a 5V supply, yet the same connection can deliver 20mA of load current when demanded. Capacitive Loads The LT1460S3-2.5 is designed to be stable with any capacitive load. With no capacitive load, the reference is ideal for fast settling or applications where PC board space is a premium. The test circuit shown in Figure 1 is used to measure the response time for various load currents and load capacitors. The 1V step from 2.5V to 1.5V produces a current step of 1mA or 100A for RL = 1k or RL = 10k. Figure 2 shows the response of the reference with no load capacitance. The reference settles to 5mV (0.2%) in 1s for a 100A pulse and to 0.2% in 2s with a 1mA step. When load capacitance is greater than 0.01F, the reference has a small amount of ringing due to the pole formed with the output impedance. Figure 3 shows the response of the reference to a 1mA and 100A load with a 0.01F load capacitor. Figure 4 shows the response with a 1F and 10F load capacitance.
VOUT CL RL VGEN 2.5V 1.5V
1460S3 F01
VIN = 5V CIN 0.1F
LT1460S3-2.5
Figure 1. Response Time Test Circuit
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2.5V VGEN 1.5V RL = 10k
VOUT
RL = 1k VOUT
1460S3 F02
Figure 2. CL = 0
2.5V VGEN 1.5V
VOUT
RL = 10k
VOUT
RL = 1k
1460S3 F03
Figure 3. CL = 0.01F
2.5V VGEN 1.5V CL = 1F
VOUT
VOUT
CL = 10F
1460S3 F03
Figure 4. IOUT = 1mA
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LT1460S3-2.5 (SOT-23)
APPLICATIONS INFORMATION
Fast Turn-On It is recommended to add a 0.1F or larger bypass capacitor to the input pin of the LT1460S3-2.5. Although this can help stability with large load currents, the main reason is for proper start-up. The LT1460S3-2.5 can start in 2s, but it is important to limit the dv/dt of the input. Under light load conditions and with a very fast input, internal nodes overslew and this requires finite recovery time. Figure 5 shows the result of no bypass capacitance on the input and no output load. In this case the supply dv/dt is 5V in 30ns which causes internal overslew, and the output does not bias to 2.5V until 500s. Figure 6 shows the effect of a 0.1F bypass capacitor which limits the input dv/dt to approximately 5V in 2s and the output settles quickly. Output Accuracy Like all references, either series or shunt, the error budget of the LT1460S3-2.5 is made up of primarily three components: initial accuracy, temperature coefficient and load regulation. Line regulation is neglected because it typically contributes only 150ppm/V, or 150V for a 1V input change. The LT1460S3-2.5 typically shifts 0.02% when soldered into a PCB, so this is also neglected. The output errors are calculated as follows for a 100A load and 0C to 70C temperature range: LT1460HCS3 Initial Accuracy = 0.2% For IOUT = 100A VOUT = (8000ppm/mA)(0.1mA)(2.5V) = 2.0mV which is 0.08% For Temperature 0C to 70C the maximum T = 70C VOUT = (20ppm/C)(70C)(2.5V) = 3.5mV which is 0.14%
VIN 5V 0V
VOUT 0V
0.2ms/DIV
1460S3 F05
Figure 5. CBYPASS = 0
VIN
VOUT
2s/DIV
1460S3 F06
Figure 6. CBYPASS = 0.1F
6
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5V 0V
W
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Total worst-case output error is: 0.2% + 0.08% + 0.14% = 0.420% Table 1 gives the worst-case accuracy for LT1460HCS3, LT1460JCS3 and LT1460KCS3 from 0C to 70C, and shows that if the LT1460HCS3 is used as a reference instead of a regulator, it is capable of 8 bits of absolute accuracy over temperature without a system calibration.
Table 1. Worst-Case Output Accuracy over Temperature
IOUT 0A 100A 10mA 20mA LT1460HCS3 0.340% 0.420% 0.840% 1.100% LT1460JCS3 0.540% 0.620% 1.040% 1.300% LT1460KCS3 0.85% 0.93% 1.35% 1.61%
LT1460S3-2.5 (SOT-23)
PACKAGE DESCRIPTION
REF
0.55 (0.022)
NOTE: GOVERNING DIMENSION IN MILLIMETERS DIMENSIONS ARE INCLUSIVE OF PLATING DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR MOLD FLASH SHALL NOT EXCEED 0.254mm
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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Dimensions in millimeters (inches) unless otherwise noted.
S3 Package 3-Lead Plastic SOT-23
(LTC DWG # 05-08-1631)
2.80 - 3.04 (0.110 - 0.120)
2.10 - 2.64 (0.083 - 0.104) 1.20 - 1.40 (0.047 - 0.060)
0.45 - 0.60 (0.017 - 0.024)
0.89 - 1.03 (0.035 - 0.041) 1.78 - 2.05 (0.070 - 0.081) 0.89 - 1.12 (0.035 - 0.044)
0.01 - 0.10 (0.0004 - 0.004)
0.09 - 0.18 (0.004 - 0.007)
0.37 - 0.51 (0.015 - 0.020)
SOT-23 0497
7
LT1460S3-2.5 (SOT-23)
TYPICAL APPLICATIONS
Boosted Output Current with No Current Limit
V + (VOUT + 1.8V) R1 220 2N2905 IN LT1460S3-2.5 OUT GND 2.5V 100mA 2F SOLID TANT IN LT1460S3-2.5 OUT GND 2.5V 100mA 2F SOLID TANT
1460S3 TA04
+
RELATED PARTS
PART NUMBER LT1019 LT1027 LT1236 LT1634 DESCRIPTION Precision Bandgap Reference Precision 5V Reference Precision Low Noise Reference Micropower Precision Shunt Reference 1.25V, 2.5V Output COMMENTS 0.05% Max, 5ppm/C Max 0.02%, 2ppm/C Max 0.05% Max, 5ppm/C Max, SO Package 0.05%, 25ppm/C Max
8
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417 q (408) 432-1900 FAX: (408) 434-0507 q TELEX: 499-3977 q www.linear-tech.com
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+
Boosted Output Current with Current Limit
V+ VOUT + 2.8V
+
47F
D1* LED
R1 220
+
8.2 2N2905 47F
+
1460S3 TA03
* GLOWS IN CURRENT LIMIT, DO NOT OMIT
Handling Higher Load Currents
5V 40mA 47F R1* 63 10mA VOUT 2.5V RL TYPICAL LOAD CURRENT = 50mA OUT GND
IN LT1460S3-2.5
*SELECT R1 TO DELIVER 80% OF TYPICAL LOAD CURRENT. LT1460 WILL THEN SOURCE AS NECESSARY TO MAINTAIN PROPER OUTPUT. DO NOT REMOVE LOAD AS OUTPUT WILL BE DRIVEN UNREGULATED HIGH. LINE REGULATION IS DEGRADED IN THIS APPLICATION
1460S3 TA05
1460S32F LT/TP 0997 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1997

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