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LT1129/LT1129-3.3/LT1129-5 Micropower Low Dropout Regulators with Shutdown
FEATURES

DESCRIPTIO
0.4V Dropout Voltage 700mA Output Current 50A Quiescent Current No Protection Diodes Needed Adjustable Output from 3.8V to 30V 3.3V and 5V Fixed Output Voltages Controlled Quiescent Current in Dropout Shutdown 16A Quiescent Current in Shutdown Stable with 3.3F Output Capacitor Reverse Battery Protection No Reverse Output Current Thermal Limiting Surface Mount SOT-223 and DD Packages
The LT(R)1129/LT1129-3.3/LT1129-5 are micropower low dropout regulators with shutdown. The devices are capable of supplying 700mA of output current with a dropout voltage of 0.4V at maximum output. Designed for use in battery-powered systems the low quiescent current, 50A operating and 16A in shutdown, make them an ideal choice. The quiescent current does not rise in dropout as it does with many other low dropout PNP regulators. Other features of the LT1129 /LT1129-3.3/LT1129-5 include the ability to operate with small output capacitors. They are stable with only 3.3F on the output while most older devices require between 10F and 100F for stability. Also the input may be connected to ground or a reverse voltage without reverse current flow from output to input. This makes the LT1129/LT1129-3.3/LT1129-5 ideal for backup power situations where the output is held high and the input is at ground or reversed. Under these conditions, only 16A will flow from the output pin to ground. The devices are available in 5-lead TO-220, 5-lead DD and 3-lead SOT-223 packages.
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
APPLICATIO S

Low Current Regulator Regulator for Battery-Powered Systems Post Regulator for Switching Supplies 5V to 3.3V Logic Regulator
TYPICAL APPLICATIO
5 1
5V Supply with Shutdown
0.6
IN LT1129-5
OUT
5V OUT 500mA
DROPOUT VOLTAGE (V)
VIN > 5.5V 4
+
2
0.5 0.4 0.3 0.2 0.1
SENSE SHDN GND 3
3.3F SOLID TANTALUM
VSHDN (PIN 4) OUTPUT < 0.25 OFF > 2.8 ON NC ON
LT1129 * TA01
0 0 0.1 0.5 0.2 0.3 0.4 OUTPUT CURRENT (A) 0.6 0.7
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Dropout Voltage
LT1129 * TA02
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LT1129/LT1129-3.3/LT1129-5
ABSOLUTE AXI U RATI GS
Input Voltage ...................................................... 30V* Output Pin Reverse Current ................................. 10mA Sense Pin Current ................................................ 10mA Adjust Pin Current ............................................... 10mA Shutdown Pin Input Voltage (Note 2) ........ 6.5V, - 0.6V Shutdown Pin Input Current (Note 2) .................. 20mA Output Short-Circuit Duration ......................... Indefinite
PACKAGE/ORDER I FOR ATIO
TOP VIEW GND GND GND GND GND GND OUT SENSE GND 1 2 3 4 5 6 7 8 9 20 GND 19 GND 18 GND 17 GND 16 GND 15 GND 14 IN 13 SHDN 12 GND 11 GND
ORDER PART NUMBER LT1129CF-3.3
TAB IS GND
GND 10
F PACKAGE 20-LEAD PLASTIC TSSOP
NOTE: ALL GROUND PINS ARE INTERNALLY CONNECTED JA 40C/ W
OBSOLETE PACKAGE
FRONT VIEW 3 TAB IS GND 2 1 OUTPUT GND VIN
ORDER PART NUMBER LT1129CST-3.3 LT1129CST-5 LT1129IST-3.3 LT1129IST-5
TAB IS GND
ST PACKAGE 3-LEAD PLASTIC SOT-223 JA 50C/ W
Consult factory for Military grade parts.
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(Note 1)
Storage Temperature Range ................ - 65C to 150C Operating Junction Temperature Range (Note 2) LT1129C-X ......................................... 0C to 125C LT1129C-X Extended Temperature Range (Note 12) ........................................ -40C to 125C LT1129I-X ...................................... -40C to 125C Lead Temperature (Soldering, 10 sec).................. 300C
* For applications requiring input voltage ratings greater than 30V, contact the factory.
FRONT VIEW 5 4 3 2 1 Q PACKAGE 5-LEAD PLASTIC DD
*PIN 2 = SENSE FOR LT1129-3.3/LT1129-5 = ADJ FOR LT1129 JA 30C/ W
TOP VIEW
VIN SHDN GND SENSE/ADJ* OUTPUT
OUTPUT 1 SENSE/ 2 ADJ* GND 3 NC 4
8 VIN 7 GND 6 GND 5 SHDN
S8 PACKAGE 8-LEAD PLASTIC SO
*PIN 2 = SENSE FOR LT1129-3.3/LT1129-5 = ADJ FOR LT1129 JA 60C/ W
ORDER PART NUMBER LT1129CQ LT1129CQ-3.3 LT1129CQ-5 LT1129IQ LT1129IQ-3.3 LT1129IQ-5
FRONT VIEW 5 4 3 2 1 T PACKAGE 5-LEAD PLASTIC TO-220
*PIN 2 = SENSE FOR LT1129-3.3/LT1129-5 = ADJ FOR LT1129 JA 50C/ W
ORDER PART NUMBER LT1129CS8 LT1129CS8-3.3 LT1129CS8-5 LT1129IS8 LT1129IS8-3.3 LT1129IS8-5
PART MARKING 1129 11293 11295 1129I 1129I3 1129I5 ORDER PART NUMBER LT1129CT LT1129CT-3.3 LT1129CT-5 LT1129IT LT1129IT-3.3 LT1129IT-5
VIN SHDN GND SENSE/ADJ* OUTPUT
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LT1129/LT1129-3.3/LT1129-5
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C.
PARAMETER Regulated Output Voltage (Notes 4, 12) CONDITIONS LT1129-3.3 LT1129-5 LT1129 (Note 5) Line Regulation (Note 12) LT1129-3.3 LT1129-5 LT1129 (Note 5) Load Regulation (Note 12) LT1129-3.3 LT1129-5 LT1129 (Note 5) Dropout Voltage (Note 6) VIN = 3.8V, IOUT = 1mA, TJ = 25C 4.3V < VIN < 20V, 1mA < IOUT < 700mA VIN = 5.5V, IOUT = 1mA, TJ = 25C 6V < VIN < 20V, 1mA < IOUT < 700mA VIN = 4.3V, IOUT = 1mA, TJ = 25C 4.8V < VIN < 20V, 1mA < IOUT < 700mA VIN = 4.8V to 20V, IOUT = 1mA VIN = 5.5V to 20V, IOUT = 1mA VIN = 4.3V to 20V, IOUT = 1mA ILOAD = 1mA to 700mA, TJ = 25C ILOAD = 1mA to 700mA ILOAD = 1mA to 700mA, TJ = 25C ILOAD = 1mA to 700mA ILOAD = 1mA to 700mA, TJ = 25C ILOAD = 1mA to 700mA

ELECTRICAL CHARACTERISTICS
MIN 3.250 3.200 4.925 4.850 3.695 3.640
TYP 3.300 3.300 5.000 5.000 3.750 3.750 1.5 1.5 1.5 6 15 6 20 6 15 0.13 0.25
MAX 3.350 3.400 5.075 5.150 3.805 3.860 10 10 10 20 30 20 30 20 30 0.20 0.25 0.35 0.45 0.45 0.60 0.55 0.70 70 450 3.5 20 45 90 300 2.8 10 25
UNITS V V V V V V mV mV mV mV mV mV mV mV mV V V V V V V V V A A mA mA mA mA nA V V A A dB
ILOAD = 10mA, TJ = 25C ILOAD = 10mA ILOAD = 100mA, TJ = 25C ILOAD = 100mA ILOAD = 500mA, TJ = 25C ILOAD = 500mA ILOAD = 700mA, TJ = 25C ILOAD = 700mA
0.37
0.45

Ground Pin Current (Note 7)
ILOAD = 0mA ILOAD = 10mA ILOAD = 100mA ILOAD = 300mA ILOAD = 500mA ILOAD = 700mA
50 310 2.0 10 25 50 150 0.25 1.2 0.75 6 15 52 64 1.2
Adjust Pin Bias Current (Notes 5, 8) Shutdown Threshold Shutdown Pin Current (Note 9) Quiescent Current in Shutdown (Note 10) Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 11)
TJ = 25C VOUT = Off to On VOUT = On to Off VSHDN = 0V VIN = 6V, VSHDN = 0V VIN - VOUT = 1V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 0.7A, TJ = 25C VIN - VOUT = 7V, TJ = 25C VIN = -20V, VOUT = 0V LT1129-3.3 LT1129-5 LT1129 (Note 5) VOUT = 3.3V, VIN = 0V VOUT = 5V, VIN = 0V VOUT = 3.8V, VIN = 0V
1.6 1.0 25 25 25
A mA A A A
16 16 16
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LT1129/LT1129-3.3/LT1129-5
ELECTRICAL CHARACTERISTICS
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The shutdown pin input voltage rating is required for a low impedance source. Internal protection devices connected to the shutdown pin will turn on and clamp the pin to approximately 7V or - 0.6V. This range allows the use of 5V logic devices to drive the pin directly. For high impedance sources or logic running on supply voltages greater than 5.5V, the maximum current driven into the shutdown pin must be limited to less than 20mA. Note 3: For junction temperatures greater than 110C, a minimum load of 1mA is recommended. For TJ > 110C and IOUT < 1mA, output voltage may increase by 1%. 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: The LT1129 is tested and specified with the adjust pin connected to the output pin. Note 6: Dropout voltage is the minimum input/output voltage required to maintain regulation at the specified output current. In dropout the output voltage will be equal to (VIN - VDROPOUT). Dropout voltage is measured between the input pin and the output pin. External voltage drops between the output pin and the sense pin will add to the dropout voltage. Note 7: Ground pin current is tested with VIN = VOUT (nominal) and a current source load. This means that the device is tested while operating in its dropout region. This is the worst case ground pin current. The ground pin current will decrease slightly at higher input voltages. Note 8: Adjust pin bias current flows into the adjust pin. Note 9: Shutdown pin current at VSHDN = 0V flows out of the shutdown pin. Note 10: Quiescent current in shutdown is equal to the sum total of the shutdown pin current (6A) and the ground pin current (9A). Note 11: Reverse output current is tested with the input pin grounded. The output pin and the sense pin are forced to the rated output voltage. This current flows into the sense pin and out of the ground pin. For the LT1129 (adjustable version) the sense pin is internally tied to the output pin. Note 12: For C-grade devices Regulated Output Voltage, Line Regulation, and Load Regulation are guaranteed over the extended temperature range of - 40C to 125C. These parameters are not tested or quality assurance sampled at -40C. They are guaranteed by design, correlation and/or inference from 25C and/or 0C tests.
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LT1129/LT1129-3.3/LT1129-5 TYPICAL PERFOR A CE CHARACTERISTICS
Guaranteed Dropout Voltage
0.7 0.6
DROPOUT VOLTAGE (V)
QUIESCENT CURRENT (A)
TJ 125C
DROPOUT VOLTAGE (V)
0.5 0.4 0.3 0.2 0.1 = TEST POINTS 0 0 0.1 0.3 0.4 0.2 0.5 OUTPUT CURRENT (A) 0.6 0.7 TJ 25C
LT1129-3.3 Quiescent Current
250 225 ILOAD = 0 RLOAD = 250 225
QUIESCENT CURRENT (A)
QUIESCENT CURRENT (A)
QUIESCENT CURRENT (A)
200 175 150 125 100 75 50 25 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 VSHDN = 0V VSHDN = OPEN (HI)
LT1129-3.3 Output Voltage
3.400 3.375 ILOAD = 1mA 5.100 5.075
ADJUST PIN VOLTAGE (V)
3.325 3.300 3.275 3.250 3.225 3.200 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125
OUTPUT VOLTAGE (V)
3.350
5.050 5.025 5.000 4.975 4.950 4.925 4.900 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125
ADJUST PIN VOLTAGE (V)
UW
1129 G02
1129 G12 1129 G06
Dropout Voltage
0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -50 A. ILOAD = 700mA B. ILOAD = 500mA C. ILOAD = 300mA D. ILOAD = 100mA E. ILOAD = 10mA A B C D E
70 60 50 40 30 20 10
Quiescent Current
VSHDN = OPEN (HI)
VSHDN = 0V
-25
50 25 0 75 TEMPERATURE (C)
100
125
0 -50
-25
50 25 0 75 TEMPERATURE (C)
100
125
1129 G10
1129 G11
LT1129-5 Quiescent Current
250 ILOAD = 0 RLOAD = 225 200 175 150 125 100 75 50 25 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
LT1129 Quiescent Current
ILOAD = 0 RLOAD = VOUT = VADJ
200 175 150 125 100 75 50 25 0 VSHDN = 0V VSHDN = OPEN (HI)
VSHDN = OPEN (HI)
VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1129 G14
1129 G13
LT1129-5 Output Voltage
3.850
ILOAD = 1mA
LT1129 Adjust Pin Voltage
3.825 3.800 3.775 3.750 3.725 3.700 3.675 3.650 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125 ILOAD = 1mA
1129 G04
1129 G05
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LT1129/LT1129-3.3/LT1129-5 TYPICAL PERFOR A CE CHARACTERISTICS
LT1129-3.3 Ground Pin Current
2.0 1.8 TJ = 25C VOUT = VSENSE RLOAD = 33 ILOAD = 100mA* 2.0 1.8 TJ = 25C VOUT = VSENSE RLOAD = 50 ILOAD = 100mA*
GROUND PIN CURRENT (mA)
GROUND PIN CURRENT (mA)
GROUND PIN CURRENT (mA)
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0
RLOAD = 66 ILOAD = 50mA*
RLOAD = 330 ILOAD = 10mA* *For VOUT = 3.3V 1 2 34567 INPUT VOLTAGE (V) 8 9 10
LT1129-3.3 Ground Pin Current
60 50 40 30 RLOAD = 6.6 ILOAD = 500mA* 20 10 0 RLOAD = 11 ILOAD = 300mA* *For VOUT = 3.3V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 TJ = 25C VOUT = VSENSE
GROUND PIN CURRENT (mA)
GROUND PIN CURRENT (mA)
GROUND PIN CURRENT (mA)
RLOAD = 4.7 ILOAD = 700mA*
Ground Pin Current
70 60
GROUND PIN CURRENT (mA)
SHUTDOWN THRESHOLD (V)
SHUTDOWN THRESHOLD (V)
50 40
VIN = 3.3V (LT1129-3.3) VIN = 5V (LT1129-5) VIN = 3.75V (LT1129) DEVICE IS OPERATING IN DROPOUT
TJ = 125C
TJ = 25C 30 20 TJ = -50C 10 0 0 0.1 0.2 0.3 0.4 0.5 OUTPUT CURRENT (A) 0.6 0.7
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1129 G18
1129 G21
LT1129-5 Ground Pin Current
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
8 9 10
LT1129 Ground Pin Current
TJ = 25C VOUT = VADJ
1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0 1 2 *For VOUT = 5V
RLOAD = 38 ILOAD = 100mA*
RLOAD = 100 ILOAD = 50mA*
RLOAD = 75 ILOAD = 50mA*
RLOAD = 500 ILOAD = 10mA*
RLOAD = 375 ILOAD = 10mA* *For VOUT = 3.75V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
34567 INPUT VOLTAGE (V)
0
1129 G19
1129 G20
LT1129-5 Ground Pin Current
60 50 40 30 20 10 0 RLOAD = 16.6 ILOAD = 300mA* *For VOUT = 5V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 TJ = 25C VOUT = VSENSE 60 50 40 30 20 10 0
LT1129 Ground Pin Current
TJ = 25C VOUT = VADJ RLOAD = 5.3 ILOAD = 700mA*
RLOAD = 7.1 ILOAD = 700mA* RLOAD = 10 ILOAD = 500mA*
RLOAD = 7.5 ILOAD = 500mA* RLOAD = 12.6 ILOAD = 300mA* *For VOUT = 3.75V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1129 G22
1129 G23
Shutdown Pin Threshold (On-to-Off)
2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125 ILOAD = 1mA 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2
Shutdown Pin Threshold (Off-to-On)
ILOAD = 700mA
ILOAD = 1mA
0 -50
-25
50 25 0 75 TEMPERATURE (C)
100
125
1129 G15
1129 G27
1129 G26
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LT1129/LT1129-3.3/LT1129-5 TYPICAL PERFOR A CE CHARACTERISTICS
Shutdown Pin Current
10
SHUTDOWN PIN INPUT CURRENT (mA)
9
SHUTDOWN PIN CURRENT (A)
VSHDN = 0V
8 7 6 5 4 3 2 1 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125
20
ADJUST PIN BIAS CURRENT (nA)
Reverse Output Current
30 25 VIN = 0V VOUT = VSENSE = 5V (LT1129-5) VOUT = VSENSE = 3.3V (LT1129-3.3) VOUT = VADJ = 3.75V (LT1129) 1.4 1.2
SHORT-CIRCUIT CURRENT (A)
20 15 10 5 0 -50
1.0 0.8 0.6 0.4 0.2 0
SHORT-CIRCUIT CURRENT (A)
OUTPUT CURRENT (A)
-25
50 25 0 75 TEMPERATURE (C)
Reverse Output Current
100 90 80 TJ = 25C, VIN = 0V VOUT = VSENSE (LT1129-3.3/LT1129-5) VOUT = VADJ (LT1129) CURRENT FLOWS INTO DEVICE LT1129
70 68
RIPPLE REJECTION (dB)
70 60 50 40 30 20 10 0 0
66 64 62 60 58 56 -50
RIPPLE REJECTION (dB)
OUTPUT CURRENT (A)
LT1129-3.3 LT1129-5
1
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345678 OUTPUT VOLTAGE (V)
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1129 G25
Shutdown Pin Input Current
25
400 350 300 250 200 150 100 50
Adjust Pin Bias Current
VADJ = VOUT = 3.75V
15
10
5
0 0 1 7 3 8 2 5 6 4 SHUTDOWN PIN VOLTAGE (V) 9
0 -50
-25
50 25 0 75 TEMPERATURE (C)
100
125
1129 G24
1129 G28
Current Limit
1.4 VOUT = 0V 1.2 1.0 0.8 0.6 0.4 0.2
Current Limit
VIN = 7V VOUT = 0V -25 50 25 0 75 TEMPERATURE (C) 100 125
100
125
0
1
4 3 2 5 INPUT VOLTAGE (V)
6
7
1129 G07
0 -50
1129 G29
1129 G08
Ripple Rejection
100
(VIN - VOUT)AVG = 1V VRIPPLE = 0.5VP-P IL = 0.7A
Ripple Rejection
90 80 70 60 50 40 30 20 10 0 COUT = 3.3F SOLID TANTALUM 10 100 1k 10k FREQUENCY (Hz) 100k 1M
1129 G01
IOUT = 500mA VIN = 6V + 50mVRMS RIPPLE
COUT = 47F SOLID TANTALUM
9
10
-25
50 25 0 75 TEMPERATURE (C)
100
125
1129 G30
1129 G03
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LT1129/LT1129-3.3/LT1129-5 TYPICAL PERFOR A CE CHARACTERISTICS
Load Regulation
0 LT1129-3.3
OUTPUT VOLTAGE DEVIATION (V)
-5
0.05 0 -0.05 -0.10
OUTPUT VOLTAGE DEVIATION (V)
LOAD REGULATION (mV)
-10 -15 -20
LT1129* LT1129-5
LOAD CURRENT (A)
-25 -30 -50
VIN = VOUT(NOMINAL) + 1V ILOAD = 1mA to 700mA *VADJ = VOUT -25 50 25 0 75 TEMPERATURE (C) 100 125
0.6 0.5 0 50 100 150 200 250 300 350 400 450 500 TIME (s)
1129 G31
LOAD CURRENT (A)
PI FU CTIO S
Input Pin: Power is supplied to the device through the input pin. The input pin should be bypassed to ground if the device is more than 6 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 LT1129 is designed to withstand reverse voltages on the input pin with respect to both ground and the output pin. In the case of a reversed input, which can happen if a battery is plugged in backwards, the LT1129 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT1129 and no reverse voltage will appear at the load. The device will protect both itself and the load. Output Pin: The output pin supplies power to the load. An output capacitor is required to prevent oscillations. See the Applications Information section for recommended value of output capacitance and information on reverse output characteristics. Shutdown Pin (SHDN): This pin is used to put the device into shutdown. In shutdown the output of the device is turned off. This pin is active low. The device will be shut down if the shutdown pin is actively pulled low. The shutdown pin current with the pin pulled to ground will be 6A. The shutdown pin is internally clamped to 7V and - 0.6V (one VBE). This allows the shutdown pin to be driven directly by 5V logic or by open collector logic with a pullup resistor. The pull-up resistor is only required to supply the leakage current of the open collector gate, normally several microamperes. Pull-up current must be limited to a maximum of 20mA. A curve of shutdown pin input current as a function of voltage appears in the Typical Performance Characteristics. If the shutdown pin is not used it can be left open circuit. The device will be active, output on, if the shutdown pin is not connected. Sense Pin: For fixed voltage versions of the LT1129 (LT1129-3.3, LT1129-5) 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 output pin. For most applications the sense pin is connected directly to the output pin at the regulator. In critical applications small voltage drops caused by the resistance (RP) of PC traces between the regulator and the load, which would normally degrade regulation, may be eliminated by connecting the sense pin to the output pin 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 15A at the nominal regulated output voltage. This pin is internally clamped to - 0.6V (one VBE).
8
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1129 G09
LT1129-5 Transient Response
0.10 VIN = 6V CIN = 3.3F COUT = 3.3F 0.2 0.1 0 -0.1 -0.2 0.7 0.5 0.3 0.1
LT1129-5 Transient Response
VIN = 6V CIN = 3.3F COUT = 47F
0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 TIME (ms)
1129 G32
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LT1129/LT1129-3.3/LT1129-5
PI FU CTIO S
Adjust Pin: For the LT1129 (adjustable version) the adjust pin is the input to the error amplifier. This pin is internally clamped to 6V and - 0.6V (one VBE). This pin has a bias current of 150nA which flows into the pin. See Bias Current curve in the Typical Performance Characteristics. The adjust pin reference voltage is equal to 3.75V referenced to ground.
RP IN 1F LT1129 SHDN GND SENSE 10F OUT
APPLICATIO S I FOR ATIO
The LT1129 is a micropower low dropout regulator with shutdown, capable of supplying 700mA of output current at a dropout voltage of 0.4V. The device operates with very low quiescent current (50A). In shutdown the quiescent current drops to only 16A. In addition to the low quiescent current the LT1129 incorporates several protection features which make it ideal for use in battery-powered systems. The device is protected against reverse input voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT1129 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The adjustable version of the LT1129 has an output voltage range of 3.75V to 30V. The output voltage is set by the ratio of two external resistors as shown in Figure 2. The device servos the output voltage to maintain the voltage at the adjust pin at 3.75V. The current in R1 is then equal to 3.75V/R1. The current in R2 is equal to the sum of the current in R1 and the adjust pin bias current. The adjust pin bias current, 150nA at 25C, flows through R2 into the adjust pin. The output voltage can be calculated according to the formula in Figure 2. The value of R1 should be less than 400k to minimize errors in the output voltage caused by the adjust pin bias current. Note that in shutdown the output is turned off and the divider current will be zero. Curves of Adjust Pin Voltage vs Temperature and Adjust Pin Bias Current vs Temperature appear in the Typical
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LT1129 * F01
Figure 1. Kelvin Sense Connection
Performance Characteristics. The reference voltage at the adjust pin has a positive temperature coefficient of approximately 15ppm/C. The adjust pin bias current has a negative temperature coefficient. These effects are small and will tend to cancel each other. The adjustable device is specified with the adjust pin tied to the output pin. This sets the output voltage to 3.75V. Specifications for output voltages greater than 3.75V will be proportional to the ratio of the desired output voltage to 3.75V (VOUT/3.75V). For example: load regulation for an output current change of 1mA to 700mA is - 6mV typical at VOUT = 3.75V. At VOUT = 12V, load regulation would be: 12V * ( - 6mV ) = ( -19mV ) 3.75V
IN LT1129 SHDN GND
OUT R2 ADJ R1
VOUT
+
LT1129 * F02
VOUT = 3.75V 1 + R2 + IADJ * R2 R1 VADJ = 3.75V IADJ = 150nA at 25C OUTPUT RANGE = 3.75V to 30V
(
)
(
)
Figure 2. Adjustable Operation
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LT1129/LT1129-3.3/LT1129-5
APPLICATIO S I FOR ATIO
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 ground pin current can be found by examining the Ground Pin Current curves in the Typical Performance Characteristics. Power dissipation will be equal to the sum of the two components listed above. The LT1129 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal load 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. Experiments have shown that the heat spreading copper layer does not need to be electrically connected to the tab of the device. The PC material can be very effective at transmitting heat between the pad area, attached to the tab of the device, and a ground or power plane layer either inside or on the opposite side of the board. Although the actual thermal resistance of the PC material is high, the length/area ratio of the thermal resistor between layers is small. Copper board stiffeners and plated through holes can also be used to spread the heat generated by power devices. The following tables list thermal resistances for each package. For the TO-220 package, thermal resistance is given for junction-to-case only since this package is usually mounted to a heat sink. Measured values of thermal resistance for several different board sizes and copper areas are listed for each package. All measurements were taken in still air on 3/32" FR-4 board with 1-oz
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copper. This data can be used as a rough guideline in estimating thermal resistance. The thermal resistance for each application will be affected by thermal interactions with other components as well as board size and shape. Some experimentation will be necessary to determine the actual value.
Table 1. Q Package, 5-Lead DD
COPPER AREA TOPSIDE* BACKSIDE 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 125 sq. mm 2500 sq. mm THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 25C/W 27C/W 35C/W * Tab of device attached to topside copper
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Table 2. ST Package, 3-Lead SOT-223
COPPER AREA TOPSIDE* BACKSIDE 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 225 sq. mm 100 sq. mm 2500 sq. mm 2500 sq. mm THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 2500 sq. mm 45C/W 45C/W 53C/W 59C/W
* Tab of device attached to topside copper
Table 3. S8 Package, 8-Lead Plastic SOIC
COPPER AREA TOPSIDE* BACKSIDE 2500 sq. mm 2500 sq. mm 1000 sq. mm 2500 sq. mm 225 sq. mm 100 sq. mm 2500 sq. mm 2500 sq. mm THERMAL RESISTANCE BOARD AREA (JUNCTION-TO-AMBIENT) 2500 sq. mm 2500 sq. mm 2500 sq. mm 2500 sq. mm 55C/W 55C/W 63C/W 69C/W
* Device attached to topside copper
T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 5C/W
LT1129/LT1129-3.3/LT1129-5
APPLICATIO S I FOR ATIO
Calculating Junction Temperature Example: Given an output voltage of 3.3V, an input voltage range of 4.5V to 5.5V, an output current range of 0mA to 500mA, 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) where, IOUT MAX = 500mA VIN MAX = 5.5V IGND at (IOUT = 500mA, VIN = 5.5V) = 25mA so, P = 500mA * (5.5V - 3.3V) + (25mA * 5.5V) = 1.24W
If we use a DD package, then the thermal resistance will be in the range of 25C/W to 35C/W depending on copper area. So the junction temperature rise above ambient will be approximately equal to: 1.24W * 30C/W = 37.2C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50C + 37.2C = 87.2C Output Capacitance and Transient Performance The LT1129 is designed to be stable with a wide range of output capacitors. The minimum recommended value is 3.3F with an ESR of 2 or less. The LT1129 is a micropower device and output transient response will be a function of output capacitance. See the Transient Response curves in the Typical Performance Characteristics. Larger values of output capacitance will decrease the peak deviations and provide improved output transient response. Bypass capacitors, used to decouple individual components powered by the LT1129, will increase the effective value of the output capacitor.
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Protection Features The LT1129 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 voltages from output to input. For fixed voltage devices the output and sense pins are tied together at the output. 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 30V. 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 that can be plugged in backwards. For fixed voltage versions of the device, the sense pin is internally clamped to one diode drop below ground. For the adjustable version of the device, the output pin is internally clamped at one diode drop below ground. If the output pin of an adjustable device, or the sense pin of a fixed voltage device, is pulled below ground, with the input open or grounded, current must be limited to less than 5mA. 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 vary depending on the conditions. Many battery-powered circuits incorporate some form of power management. The following information will help optimize battery life. Table 3 summarizes the following information. The reverse output current will follow the curve in Figure 3 when the input pin is pulled to ground. This current flows through the output pin to ground. The state of the shutdown pin will have no effect on output current when the input pin is pulled to ground.
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LT1129/LT1129-3.3/LT1129-5
APPLICATIO S I FOR ATIO
In some applications it may be necessary to leave the input to the LT1129 unconnected when the output is held high. This can happen when the LT1129 is powered from a rectified AC source. If the AC source is removed, then the input of the LT1129 is effectively left floating. The reverse output current also follows the curve in Figure 3 if the input pin is left open. The state of the shutdown pin will have no effect on the reverse output current when the input pin is floating.
100 TJ = 25C 90 VIN = 0V VSENSE = VOUT 80 CURRENT FLOWS 70 INTO DEVICE 60 50 40 30 20 10 0 0 1 2 LT1129-5 LT1129-3.3 LT1129
OUTPUT PIN CURRENT (A)
INPUT CURRENT (A)
345678 OUTPUT VOLTAGE (V)
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10
1129 F03
Figure 3. Reverse Output Current
Table 4. Fault Conditions
INPUT PIN < VOUT (Nominal) < VOUT (Nominal) Open Open SHDN PIN Open (Hi) Grounded Open (Hi) Grounded OUTPUT PIN Forced to VOUT (Nominal) Forced to VOUT (Nominal) Forced to VOUT (Nominal) Forced to VOUT (Nominal) Reverse Output Current 15A (See Figure 3) Input Current 1A (See Figure 4) Reverse Output Current 15A (See Figure 3) Input Current 1A (See Figure 4) Reverse Output Current 15A (See Figure 3) Reverse Output Current 15A (See Figure 3)
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When the input of the LT1129 is forced to a voltage below its nominal output voltage and its output is held high, the reverse output current will still follow the curve shown in Figure 3. This can happen if the input of the LT1129 is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or by a second regulator circuit. When the input pin is forced below the output pin or the output pin is pulled above the input pin, the input current will typically drop to less than 2A (see Figure 4). The state of the shutdown pin will have no effect on the reverse output current when the output is pulled above the input.
5 VOUT = 3.3V (LT1129-3.3) VOUT = 5V (LT1129-5) 4 3 2 1 0 0 1 3 2 INPUT VOLTAGE (V) 4 5
1129 F04
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Figure 4. Input Current
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LT1129/LT1129-3.3/LT1129-5
PACKAGE DESCRIPTIO U
F Package 20-Lead Plastic TSSOP (4.4mm)
(LTC DWG # 05-08-1650)
6.40 - 6.60* (.252 - .260) 1.05 0.10 20 19 18 17 16 15 14 13 12 11 4.50 0.10 6.40 (.252) BSC 0.65 BSC 1 2 3 4 5 6 7 8 9 10 1.10 (.0433) MAX
0 - 8 0.25 REF
6.60 0.10
0.45 0.05
RECOMMENDED SOLDER PAD LAYOUT 4.30 - 4.50** (.169 - .177)
0.09 - 0.20 (.0035 - .0079)
0.50 - 0.75 (.020 - .030)
0.65 (.0256) BSC
NOTE: 1. CONTROLLING DIMENSION: MILLIMETERS MILLIMETERS 2. DIMENSIONS ARE IN (INCHES) 3. DRAWING NOT TO SCALE *DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED .152mm (.006") PER SIDE
0.19 - 0.30 (.0075 - .0118) TYP
0.05 - 0.15 (.002 - .006)
F20 TSSOP 0204
OBSOLETE PACKAGE
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LT1129/LT1129-3.3/LT1129-5
PACKAGE DESCRIPTIO U
Q Package 5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
.060 (1.524) TYP .390 - .415 (9.906 - 10.541) 15 TYP .165 - .180 (4.191 - 4.572) .045 - .055 (1.143 - 1.397) .330 - .370 (8.382 - 9.398)
.256 (6.502)
.060 (1.524)
.060 (1.524)
.183 (4.648)
.059 (1.499) TYP
(
+.008 .004 -.004 +0.203 0.102 -0.102
)
.075 (1.905) .300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +.012 .143 -.020 +0.305 3.632 -0.508 .067 (1.702) .028 - .038 BSC (0.711 - 0.965) TYP .013 - .023 (0.330 - 0.584)
.095 - .115 (2.413 - 2.921)
.050 .012 (1.270 0.305)
Q(DD5) 0502
(
)
.420
.080
.420 .276
.350 .205 .565
.325 .565
.320 .090 .067 .042 .067 .090 .042
RECOMMENDED SOLDER PAD LAYOUT NOTE: 1. DIMENSIONS IN INCH/(MILLIMETER) 2. DRAWING NOT TO SCALE
RECOMMENDED SOLDER PAD LAYOUT FOR THICKER SOLDER PASTE APPLICATIONS
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LT1129/LT1129-3.3/LT1129-5
PACKAGE DESCRIPTIO U
(LTC DWG # 05-08-1610)
.189 - .197 (4.801 - 5.004) NOTE 3 8 7 6 5 .053 - .069 (1.346 - 1.752) .004 - .010 (0.101 - 0.254) .228 - .244 (5.791 - 6.197) .150 - .157 (3.810 - 3.988) NOTE 3 .014 - .019 (0.355 - 0.483) TYP .010 - .020 x 45 (0.254 - 0.508) .008 - .010 (0.203 - 0.254) 0- 8 TYP .050 (1.270) BSC 1 2 3 4 .016 - .050 (0.406 - 1.270)
SO8 0303
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
.045 .005 .050 BSC
.245 MIN
.160 .005
.030 .005 TYP
RECOMMENDED SOLDER PAD LAYOUT
NOTE: 1. DIMENSIONS IN
INCHES (MILLIMETERS) 2. DRAWING NOT TO SCALE
3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS. MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)
ST Package 3-Lead Plastic SOT-223
(LTC DWG # 05-08-1630)
.248 - .264 (6.30 - 6.71) .114 - .124 (2.90 - 3.15) .059 MAX .129 MAX
.264 - .287 (6.70 - 7.30) .130 - .146 (3.30 - 3.71)
.248 BSC
.039 MAX
.059 MAX .090 BSC
.181 MAX .0905 (2.30) BSC .033 - .041 (0.84 - 1.04)
RECOMMENDED SOLDER PAD LAYOUT
10 - 16 .071 (1.80) MAX 10 MAX .010 - .014 (0.25 - 0.36)
10 - 16 .024 - .033 (0.60 - 0.84) .181 (4.60) BSC .012 (0.31) MIN .0008 - .0040 (0.0203 - 0.1016)
ST3 (SOT-233) 0502
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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.
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LT1129/LT1129-3.3/LT1129-5
TYPICAL APPLICATIO U
T Package 5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
.147 - .155 (3.734 - 3.937) DIA .230 - .270 (5.842 - 6.858) .460 - .500 (11.684 - 12.700) .570 - .620 (14.478 - 15.748) .330 - .370 (8.382 - 9.398) .700 - .728 (17.78 - 18.491) .620 (15.75) TYP .165 - .180 (4.191 - 4.572) .045 - .055 (1.143 - 1.397) SEATING PLANE .152 - .202 .260 - .320 (3.861 - 5.131) (6.60 - 8.13) .095 - .115 (2.413 - 2.921) .155 - .195* (3.937 - 4.953) .013 - .023 (0.330 - 0.584) BSC .067 (1.70) .028 - .038 (0.711 - 0.965) .135 - .165 (3.429 - 4.191) * MEASURED AT THE SEATING PLANE
T5 (TO-220) 0801
.390 - .415 (9.906 - 10.541)
RELATED PARTS
PART NUMBER LT1121 LT1761 LT1762 LT1962 LT1763 LT1963 LT1764 DESCRIPTION 150mA LDO Micropower Regulator 100mA Low Noise, LDO Micropower Regulator 150mA Low Noise, LDO Micropower Regulator 300mA Low Noise, LDO Micropower Regulator 500mA Low Noise, LDO Micropower Regulator 1.5A Low Noise, Fast Transient, LDO Regulator 3A Low Noise, Fast Transient, LDO Regulator COMMENTS 30A IQ, SOT-223 Package 20A IQ, 20VRMS Noise 25A IQ, 20VRMS Noise 30A IQ, 20VRMS Noise 30A IQ, 20VRMS Noise 340mV Dropout Voltage, 40VRMS Noise 340mV Dropout Voltage, 40VRMS Noise
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
LT/TP 0205 1K REV C * PRINTED IN USA
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 1994

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