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LT1529 LT1529-3.3/LT1529-5 3A Low Dropout Regulators with Micropower Quiescent Current and Shutdown DESCRIPTIO
The LT (R)1529/LT1529-3.3/LT1529-5 are 3A low dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 3A of output current with a dropout voltage of 0.6V. 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 is well controlled; it does not rise in dropout as it does with many other low dropout PNP regulators. Other features of the LT1529 /LT1529-3.3/LT1529-5 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. Small ceramic capacitors can be used, enhancing manufacturabiltiy. Also the input may be connected to voltages lower than the output voltage, including negative voltages, without reverse current flow from output to input. This makes the LT1529/LT1529-3.3/LT1529-5 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 and 5-lead DD packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
FEATURES
s s s s s s s s s s s s
Dropout Voltage: 0.6V at IOUT = 3A Output Current: 3A Quiescent Current: 50A No Protection Diodes Needed Adjustable Output from 3.8V to 14V 3.3V and 5V Fixed Output Voltages Controlled Quiescent Current in Dropout Shutdown IQ = 16A Stable with 3.3F Output Capacitor Reverse Battery Protection No Reverse Current Thermal Limiting
APPLICATIO S
s s s s
High Efficiency Regulator Regulator for Battery-Powered Systems Post Regulator for Switching Supplies 5V to 3.3V Logic Regulator
TYPICAL APPLICATIO
5 VIN > 5.5V
0.6
5V Supply with Shutdown
VIN OUTPUT 1
0.5
LT1529-5 4 SHDN SENSE GND 3 2
+
3.3F SOLID TANT
5V 3A
DROPOUT VOLTAGE (V)
0.4 0.3 0.2 0.1
VSHDN (PIN 4) < 0.25 > 2.8 NC
OUTPUT OFF ON ON
0
LT1529 * TA01
0
0.5
U
U
U
Dropout Voltage
1.0 1.5 2.0 OUTPUT CURRENT (A)
2.5
3.0
LT1529 * TA02
1
LT1529 LT1529-3.3/LT1529-5 ABSOLUTE AXI U RATI GS
Input Voltage ...................................................... 15V* OUTPUT Pin Reverse Current .............................. 10mA SENSE Pin Current .............................................. 10mA ADJ Pin Current ................................................... 10mA SHDN Pin Input Voltage (Note 2) .............. 6.5V, - 0.6V SHDN Pin Input Current (Note 2) .......................... 5mA
PACKAGE/ORDER I FOR ATIO
FRONT VIEW 5 4 3 2 1 VIN SHDN GND SENSE/ADJ* OUTPUT
ORDER PART NUMBER LT1529CQ LT1529CQ-3.3 LT1529CQ-5 LT1529IQ LT1529IQ-3.3 LT1529IQ-5
TAB IS GND
TAB IS GND
Q PACKAGE 5-LEAD PLASTIC DD PAK
*PIN 2 = SENSE FOR LT1529-3.3/LT1529-5 = ADJ FOR LT1529 TJMAX = 125C, JA 30C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25C. (Note 3)
PARAMETER Regulated Output Voltage (Note 4) CONDITIONS LT1529-3.3 LT1529-5 LT1529 (Note 5) Line Regulation LT1529-3.3 LT1529-5 LT1529 (Note 5) Load Regulation LT1529-3.3 LT1529-5 LT1529 (Note 5) Dropout Voltage (Note 6) VIN = 3.8V, IOUT = 1mA, TJ = 25C 4.3V < VIN < 15V, 1mA < IOUT < 3A VIN = 5.5V, IOUT = 1mA, TJ = 25C 6V < VIN < 15V, 1mA < IOUT < 3A VIN = 4.3V, IOUT = 1mA, TJ = 25C 4.8V < VIN < 15V, 1mA < IOUT < 3A VIN = 3.8V to 15V, IOUT = 1mA VIN = 5.5V to 15V, IOUT = 1mA VIN = 4.3V to 15V, IOUT = 1mA ILOAD = 1mA to 3A, VIN = 4.3V, TJ = 25C ILOAD = 1mA to 3A, VIN = 4.3V ILOAD = 1mA to 3A, VIN = 6V, TJ = 25C ILOAD = 1mA to 3A, VIN = 6V ILOAD = 1mA to 3A, VIN = 4.8V, TJ = 25C ILOAD = 1mA to 3A, VIN = 4.8V
q q q q q q q q q q
ILOAD = 10mA, TJ = 25C ILOAD = 10mA ILOAD = 100mA, TJ = 25C ILOAD = 100mA
2
U
U
W
WW
U
W
(Note 1)
Output Short-Circuit Duration ......................... Indefinite Storage Temperature Range ................ - 65C to 150C Operating Junction Temperature Range Commercial .......................................... 0C to 125C Industrial ......................................... - 45C to 125C Lead Temperature (Soldering, 10 sec).................. 300C
*For
applications requiring input voltage ratings greater than 15V, contact the factory.
FRONT VIEW 5 4 3 2 1 T PACKAGE 5-LEAD PLASTIC TO-220 *PIN 2 = SENSE FOR LT1529-3.3/LT1529-5 = ADJ FOR LT1529 TJMAX = 125C, JA 50C/ W VIN SHDN GND SENSE/ADJ* OUTPUT
ORDER PART NUMBER LT1529CT LT1529CT-3.3 LT1529CT-5 LT1529IT LT1529IT-3.3 LT1529IT-5
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 5 12 5 12 5 12 110 200
MAX 3.350 3.400 5.075 5.150 3.805 3.860 10 10 10 20 30 20 30 20 30 180 250 300 400
UNITS V V V V V V mV mV mV mV mV mV mV mV mV mV mV mV mV
q
LT1529 LT1529-3.3/LT1529-5
ELECTRICAL CHARACTERISTICS
PARAMETER Dropout Voltage (Note 6)
The q denotes specifications which apply over the operating temperature range, otherwise specificatons are at TA = 25C. (Note 3)
CONDITIONS ILOAD = 700mA, TJ = 25C ILOAD = 700mA ILOAD = 1.5A, TJ = 25C ILOAD = 1.5A ILOAD = 3A, TJ = 25C ILOAD = 3A ILOAD = 0mA, TJ = 25C ILOAD = 0mA, TJ = 125C (Note 8) ILOAD = 100mA, TJ = 25C ILOAD = 100mA, TJ = 125C (Note 8) ILOAD = 700mA ILOAD = 1.5A ILOAD = 3A TJ = 25C VOUT = Off to On VOUT = On to Off VSHDN = 0V VIN = VOUT (Nominal) + 1V, VSHDN = 0V VIN - VOUT = 1V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 1.5A VIN - VOUT = 7V, TJ = 25C VIN = VOUT (Nominal) + 1.5V, VOUT = - 0.1V VIN = - 15V, VOUT = 0V LT1529-3.3 VOUT = 3.3V, VIN = 0V LT1529-5 VOUT = 5V, VIN = 0V LT1529 (Note 6) VOUT = 3.8V, VIN = 0V MIN
q
TYP 320 430
q
600
q
GND Pin Current (Note 7)
q q q q q q q
ADJ Pin Bias Current (Notes 5, 9) Shutdown Threshold SHDN Pin Current (Note 10) Quiescent Current in Shutdown (Note 11) Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 12)
0.25
50 400 0.6 1.0 5.5 20 80 150 1.20 0.75 4.5 15 62 5 4.7
MAX 430 550 550 700 750 950 100 1.0 12 40 160 300 2.8 10 30
UNITS mV mV mV mV mV mV A A mA mA mA mA mA nA V V A A dB A A mA A A A
50
q q
3.2
1.0 16 16 16
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The SHDN pin input voltage rating is required for a low impedance source. Internal protection devices connected to the SHDN 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 SHDN pin must be limited to less than 5mA. Note 3: The device is tested under pulse load conditions such that TJ = TA. 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 LT1529 is tested and specified with the ADJ 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).
Note 7: GND 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 GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 8: GND pin current will rise at TJ > 75C. This is due to internal circuitry designed to compensate for leakage currents in the output transistor at high temperatures. This allows quiescent current to be minimized at lower temperatures, yet maintain output regulation at high temperatures with light loads. See quiescent current curve in typical performance characteristics. Note 9: ADJ pin bias current flows into the ADJ pin. Note 10: SHDN pin current at VSHDN = 0V flows out of the SHDN pin. Note 11: Quiescent current in shutdown is equal to the sum total of the SHDN pin current (5A) and the GND pin current (10A). Note 12: Reverse output current is tested with the VIN pin grounded and the OUTPUT pin forced to the rated output voltage. This current flows into the OUTPUT pin and out of the GND pin.
3
LT1529 LT1529-3.3/LT1529-5
TYPICAL PERFOR A CE CHARACTERISTICS
Guaranteed Dropout Voltage
1.0 0.9 DROPOUT VOLTAGE (V) DROPOUT VOLTAGE (V) 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 = TEST POINT 0.5 1.5 2.0 1.0 OUTPUT CURRENT (A) 2.5 3.0 0.1 F 0 - 50 - 25 0 50 75 25 TEMPERATURE (C) 100 125 0.8 0.7 0.6 0.5 B 0.4 0.3 0.2 C D E A: ILOAD = 3A E: ILOAD = 100mA B: ILOAD = 1.5A F: ILOAD = 10mA C: ILOAD = 700mA D: ILOAD = 300mA A
QUIESCENT CURRENT (A)
LT1529-3.3 Quiescent Current
250 225 QUIESCENT CURRENT (A) 200 175 150 125 100 75 50 25 0 0 1 2 VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10 VSHDN = OPEN (HIGH) ILOAD = 0 RL = QUIESCENT CURRENT (A) 250 225 200 175 150 125 100 75 50 25 0
QUIESCENT CURRENT (A)
LT1529-3.3 Output Voltage
3.400 3.375 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 3.350 3.325 3.300 3.275 3.250 3.225 3.200 - 50 - 25 0 75 50 25 TEMPERATURE (C) 100 125 ILOAD = 1mA 5.100 5.075
5.025 5.000 4.975 4.950 4.925 4.900 -50 -25 0 75 50 25 TEMPERATURE (C) 100 125
ADJ PIN VOLTAGE (V)
4
UW
Dropout Voltage
250
Quiescent Current
VIN = 6V RL = 200
150
100 VSHDN = OPEN 50 VSHDN = 0V
0 - 50 - 25
50 25 0 75 TEMPERATURE (C)
100
125
LT1529 * G01
LT1529 * G02
LT1529 * G03
LT1529-5 Quiescent Current
250 ILOAD = 0 RL = 225 200 175 150 125 100 75 50 25 8 9 10 0
LT1529 Quiescent Current
ILOAD = 0 RL = VOUT = VADJ
VSHDN = OPEN (HIGH)
VSHDN = OPEN (HIGH)
VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V)
VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
LT1529 * G04
LT1529 * G05
LT1529 * G06
LT1529-5 Output Voltage
3.850 ILOAD = 1mA 3.825 3.800 3.775 3.750 3.725 3.700 3.675 5.050
LT1529 ADJ Pin Voltage
ILOAD = 1mA
3.650 - 50 - 25
0
75 50 25 TEMPERATURE (C)
100
125
LT1529 * G07
LT1529 * G08
LT1529 * G09
LT1529 LT1529-3.3/LT1529-5
TYPICAL PERFOR A CE CHARACTERISTICS
LT1529-3.3 GND Pin Current
5.0 4.5 4.0
GND PIN CURRENT (mA)
TJ = 25C VOUT = VSENSE *FOR VOUT = 3.3V
3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 2
GND PIN CURRENT (mA)
3.5 3.0 2.5 2.0 1.5 1.0 0.5 RLOAD = 500 ILOAD = 10mA*
GND PIN CURRENT (mA)
RLOAD = 6.6 ILOAD = 500mA*
RLOAD = 330 ILOAD = 10mA* RLOAD = 11 ILOAD = 300mA* RLOAD = 33 ILOAD = 100mA*
34567 INPUT VOLTAGE (V)
LT1529-3.3 GND Pin Current
100 90 80 TJ = 25C *FOR VOUT = 3.3V VOUT = VSENSE RLOAD = 1.1 ILOAD = 3A*
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
70 60 50 40 30 20 10 0 0
RLOAD = 4.7 ILOAD = 700mA* RLOAD = 2.2 ILOAD = 1.5A*
1
2
34567 INPUT VOLTAGE (V)
GND Pin Current
100 90 GND PIN CURRENT (mA) 80 70 60 50 40 30 20 10 0 0 0.5 1.5 2.0 1.0 OUTPUT CURRENT (A) 2.5 3.0 TJ = 125C TJ = - 50C
2.0
SHDN THRESHOLD (V)
SHDN THRESHOLD (V)
VIN = 3.75V (LT1529) VIN = 3.3V (LT1529-3.3) VIN = 5V (LT1529-5) DEVICE IS OPERATING IN DROPOUT TJ = 25C
UW
8 9 10
LT1529 * G10
LT1529-5 GND Pin Current
5.0 TJ = 25C 4.5 VOUT = VSENSE *FOR VOUT = 5V 4.0
5.0
LT1529 GND Pin Current
TJ = 25C 4.5 VOUT = VADJ *FOR VOUT = 4.0 3.75V 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 RLOAD = 38 ILOAD = 100mA*
RLOAD = 10 ILOAD = 500mA*
RLOAD = 7.5 ILOAD = 500mA* RLOAD = 375 ILOAD = 10mA* RLOAD = 12.5 ILOAD = 300mA*
RLOAD = 16.6 ILOAD = 300mA* RLOAD = 50 ILOAD = 100mA*
0
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
LT1529 * G11
LT1529 * G12
LT1529-5 GND Pin Current
100 90 80 70 60 50 40 30 20 10
8 9
LT1529 GND Pin Current
100 RLOAD = 1.7 ILOAD = 3A* TJ = 25C 90 VOUT = VADJ *FOR VOUT = 3.75V 80 70 60 50 40 30 20 10 0 RLOAD = 5.3 ILOAD = 700mA* RLOAD = 2.5 ILOAD = 1.5A* RLOAD = 1.25 ILOAD = 3A*
TJ = 25C VOUT = VSENSE *FOR VOUT = 5V
RLOAD = 7.1 ILOAD = 700mA*
RLOAD = 3.3 ILOAD = 1.5A*
0
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
LT1529 * G13
LT1529 * G14
LT1529 * G15
SHDN Pin Threshold (On-to-Off)
2.0 ILOAD = 1mA 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 50 25 0 75 TEMPERATURE (C) 100 125 1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 - 50 -25
SHDN Pin Threshold (Off-to-On)
ILOAD = 3A
ILOAD = 1mA
0 -50 -25
50 25 0 75 TEMPERATURE (C)
100
125
LT1529 * G16
LT1529 * G17
LT1529 * G18
5
LT1529 LT1529-3.3/LT1529-5
TYPICAL PERFOR A CE CHARACTERISTICS
SHDN Pin Current
10 9
SHDN PIN CURRENT (A)
VSHDN = 0V
SHDN PIN INPUT CURRENT (mA)
ADJ PIN BIAS CURRENT (nA)
8 7 6 5 4 3 2 1 0 - 50 -25 50 25 0 75 TEMPERATURE (C) 100 125
Reverse Output Current
150 125
SHORT-CIRCUIT CURRENT (A)
100 75 50 25 0 - 50 - 25
4 3 2 1 0
SHORT-CIRCUIT CURRENT (A)
OUTPUT CURRENT (A)
50 25 75 0 TEMPERATURE (C)
Reverse Output Current
100 90 80 OUTPUT CURRENT (A) 70 60 50 40 30 20 10 0 0 1 2 LT1529-3.3 LT1529-5 TJ = 25C, VIN = 0V VOUT = VSENSE (LT1529-3.3/LT1529-5) VOUT = VADJ (LT1529) CURRENT FLOWS INTO DEVICE LT1529
62 60 RIPPLE REJECTION (dB) 58 56 54 52 50
RIPPLE REJECTION (dB)
345678 OUTPUT VOLTAGE (V)
6
UW
LT1529 * G19
SHDN Pin Input Current
25
ADJ Pin Bias Current
500 450 VADJ = VOUT = 3.75V
20
400 350 300 250 200 150 100 50
15
10
5
0 0 1 2 7 3 5 6 4 SHDN PIN VOLTAGE (V) 8 9
0 -50 -25
50 25 0 75 TEMPERATURE (C)
100
125
LT1529 * G20
LT1529 * G21
Current Limit
6 VOUT = 0V 5 5 4 3 2 1 6
Current Limit
VIN = 7V VOUT = 0V
100
125
0
1
4 3 5 2 INPUT VOLTAGE (V)
6
7
0 - 50 - 25
50 25 75 0 TEMPERATURE (C)
100
125
LT1529 * G22
LT1529 * G23
LT1529 * G24
Ripple Rejection
100
Ripple Rejection
(VIN - VOUT)AVG = 1V VRIPPLE = 0.5VP-P ILOAD = 1.5A f = 120Hz
90 80 70 60 50 40 30 20 10 0 COUT = 3.3F SOLID TANT IOUT = 1.5A VIN = VOUT (NOMINAL) + 1 + 50mVRMS RIPPLE COUT = 47F SOLID TANT
9
10
48 - 50 - 25
50 25 75 0 TEMPERATURE (C)
100
125
10
100
1k 10k FREQUENCY (Hz)
100k
LT1529 * G27
LT1529 * G25
LT1529 * G26
LT1529 LT1529-3.3/LT1529-5
TYPICAL PERFOR A CE CHARACTERISTICS
Load Regulation
5 OUTPUT VOLTAGE DEVIATION (V) 0 LOAD REGULATION (mV) -5 -10 -15 -20 VIN = VOUT (NOMINAL) + 1V ILOAD = 100mA to 3A VADJ = VOUT 50 25 75 0 TEMPERATURE (C) 100 125 LT1529-3.3 LT1529 OUTPUT VOLTAGE DEVIATION (V) LT1529-5
0.2 0.1 0 - 0.1 - 0.2 VIN = 6V CIN = 3.3F TANT COUT = 47F TANT
LOAD CURRENT (A)
3 2 1 0 100 200 300 400 500 600 700 800 900 1000 TIME (s)
LT1529 * G29
LOAD CURRENT (A)
-25 - 50 - 25
PI FU CTIO S
OUTPUT (Pin 1): OUTPUT Pin. The OUTPUT pin supplies power to the load. A minimum output capacitor of 3.3F is required to prevent oscillations. Larger values will be required to optimize transient response for large load current deltas. See the Applications Information section for further information on output capacitance and reverse output characteristics. SENSE (Pin 2): SENSE Pin. For fixed voltage versions of the LT1529 (LT1529-3.3, LT1529-5) 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). ADJ (Pin 2): Adjust Pin. For the LT1529 (adjustable version) the ADJ pin is the input to the error amplifier. This
5 VIN OUTPUT 1 RP LT1529-5
UW
LT1529 * G28
LT1529-5 Transient Response
0.2 0.1 0 - 0.1 - 0.2
LT1529-5 Transient Response
VIN = 6V CIN = 10F TANT COUT = 4.7F TANT
3 2 1 0 20 40 60 80 100 120 140 160 180 200 TIME (s)
LT1529 * G30
U
U
U
+
VIN
4
SHDN SENSE GND 3
2
+
LOAD
RP
LT1529 * F01
Figure 1. Kelvin Sense Connection
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 ADJ pin reference voltage is equal to 3.75V referenced to ground. SHDN (Pin 4): Shutdown Pin. 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 SHDN pin is actively pulled low. The SHDN pin current with the pin pulled to ground will be 6A. The SHDN pin is internally clamped to 7V and - 0.6V (one VBE). This allows the SHDN pin to be driven directly by 5V logic or by open-collector logic with a pull-up 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 5mA. A curve of SHDN pin input current as a
7
LT1529 LT1529-3.3/LT1529-5 PI FU CTIO S
function of voltage appears in the Typical Performance Characteristics. If the SHDN pin is not used it can be left open circuit. The device will be active, output on, if the SHDN pin is not connected. VIN (Pin 5): Input Pin. Power is supplied to the device through the VIN pin. The VIN pin should be bypassed to ground 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 LT1529 is designed to withstand reverse voltages on the VIN pin with respect to ground and OUTPUT pin. In the case of a reversed input, which can happen if a battery is plugged in backwards, the LT1529 will act as if there is a diode in series with its input. There will be no reverse current flow into the LT1529 and no reverse voltage will appear at the load. The device will protect both itself and the load.
APPLICATI
S I FOR ATIO
The LT1529 is a 3A low dropout regulator with micropower quiescent current and shutdown capable of supplying 3A of output current at a dropout voltage of 0.6V. 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 LT1529 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 LT1529 acts like it has a diode in series with its output and prevents reverse current flow. Adjustable Operation The adjustable version of the LT1529 has an output voltage range of 3.75V to 14V. 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 ADJ 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 ADJ pin bias current. The ADJ pin bias current, 150nA at 25C, flows through R2 into the ADJ 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 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
8
U
W
U
U
UO
U
U
5 VIN
VIN
OUTPUT LT1529
1 R2 2 R1
+
VOUT
4
SHDN SENSE GND 3
VOUT = 3.75V 1 + R2 + (IADJ x R2) R1 VADJ = 3.75V IADJ = 150nA AT 25C OUTPUT RANGE = 3.3V TO 14V
()
LT1529 * F02
Figure 2. Adjustable Operation
Bias Current vs Temperature appear in the Typical Performance Characteristics. The reference voltage at the ADJ pin has a positive temperature coefficient of approximately 15ppm/C. The ADJ pin bias current has a negative temperature coefficient. These effects will tend to cancel each other. The adjustable device is specified with the ADJ pin tied to the OUTPUT pin. This sets the output voltage to 3.75V. Specifications for output voltage 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 3A is - 0.5mV typical at VOUT = 3.75V. At VOUT = 12V, load regulation would be: 12V ( - 0.5 mV) = ( -1.6mV ) 3.75V
LT1529 LT1529-3.3/LT1529-5
APPLICATI
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 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 LT1529 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 copper areas are listed for the DD package. All measurements were taken in still air on 3/32" FR-4 board with 1-oz copper. This data can be used as a rough guideline in estimating thermal resis-
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tance. 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 23C/W 25C/W 33C/W * Device is mounted on topside.
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T Package, 5-Lead TO-220
Thermal Resistance (Junction-to-Case) = 2.5C/W
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) = 3.6mA so, P = 500mA * (5.5V - 3.3V) + (3.6mA * 5.5V) = 1.12W
If we use a DD package, then the thermal resistance will be in the range of 23C/W to 33C/W depending on copper area. So the junction temperature rise above ambient will be approximately equal to: 1.12W * 28C/W = 31.4C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50C + 31.4C = 81.4C Output Capacitance and Transient Performance The LT1529 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 LT1529 is a
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LT1529 LT1529-3.3/LT1529-5
APPLICATI S I FOR ATIO
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 for larter load current deltas. Bypass capacitors, used to decouple individual components powered by the LT1529, will increase the effective value of the output capacitor. Protection Features The LT1529 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. 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 15V. 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
Table 2. Fault Conditions
VIN PIN < VOUT (Nominal) < VOUT (Nominal) Open Open 0.8V 0.8V >1.5V - 15V < VIN < 15V SHDN PIN Open (High) Grounded Open (High) Grounded Open (High) Grounded Open (High) Grounded OUTPUT/SENSE PINS Forced to VOUT (Nominal) Forced to VOUT (Nominal) > 1V > 1V 0V 0V 0V 0V 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 Peak (See Figure 3) Reverse Output Current 15A (See Figure 3) Output Current = 0 Output Current = 0 Output Current = Short-Circuit Current Output Current = 0
OUTPUT CURRENT (A)
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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 2 summarizes the following information. The reverse output current will follow the curve in Figure 3 when the input is pulled to ground. This current flows through the device to ground. The state of the SHDN pin will have no effect on output current when the VIN pin is pulled to ground.
100 90 80 70 60 50 40 30 20 10 0 0 1 2 LT1529-3.3 LT1529-5 TJ = 25C, VIN = 0V VOUT = VSENSE (LT1529-3.3/LT1529-5) VOUT = VADJ (LT1529) CURRENT FLOWS INTO DEVICE LT1529 345678 OUTPUT VOLTAGE (V) 9 10
LT1529 * F03
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Figure 3. Reverse Output Current
LT1529 LT1529-3.3/LT1529-5
APPLICATI S I FOR ATIO
In some applications it may be necessary to leave the input to the LT1529 unconnected when the output is held high. This can happen when the LT1529 is powered from a rectified AC source. If the AC source is removed, then the input of the LT1529 is effectively left floating. The reverse output current also follows the curve in Figure 3 if the VIN pin is left open. The state of the SHDN pin will have no effect on the reverse output current when the VIN pin is floating. When the input of the LT1529 is forced to a voltage below its nominal output voltage and its output is held high, the output current will follow the curve shown in Figure 3 . This can happen if the input of the LT1529 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 VIN pin is forced below the OUTPUT pin or the OUTPUT pin is pulled above the VIN pin, the input current
INPUT CURRENT (A)
PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
0.256 (6.502)
0.060 (1.524)
0.060 (1.524) TYP
0.060 (1.524)
0.183 (4.648)
0.330 - 0.370 (8.382 - 9.398)
0.075 (1.905) 0.300 (7.620) BOTTOM VIEW OF DD PAK HATCHED AREA IS SOLDER PLATED COPPER HEAT SINK +0.012 0.143 -0.020 0.057 - 0.077 (1.447 - 1.955) 0.028 - 0.038 (0.711 - 0.965) 0.013 - 0.023 (0.330 - 0.584)
(
+0.305 3.632 -0.508
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 circuits as described herein will not infringe on existing patent rights.
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will typically drop to less than 2A (see Figure 4). The state of the SHDN pin will have no effect on the reverse output current when the output is pulled above the input.
5 VOUT = 3.3V (LT1529-3.3) VOUT = 5V (LT1529-5) 4 LT1529-3.3 3 LT1529-5 2 1 0 0 1 3 2 INPUT VOLTAGE (V) 4 5
LT1529 * F04
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Figure 4. Input Current
Q Package 5-Lead Plastic DD Pak
(LTC DWG # 05-08-1461)
0.390 - 0.415 (9.906 - 10.541) 15 TYP
0.165 - 0.180 (4.191 - 4.572)
0.045 - 0.055 (1.143 - 1.397) +0.008 0.004 -0.004
0.059 (1.499) TYP
(
+0.203 0.102 -0.102
)
0.095 - 0.115 (2.413 - 2.921) 0.050 0.012 (1.270 0.305)
)
Q(DD5) 0396
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LT1529 LT1529-3.3/LT1529-5 PACKAGE DESCRIPTIO U
Dimensions in inches (millimeters) unless otherwise noted. T Package 5-Lead Plastic TO-220 (Standard)
(LTC DWG # 05-08-1421)
0.390 - 0.415 (9.906 - 10.541)
0.147 - 0.155 (3.734 - 3.937) DIA 0.230 - 0.270 (5.842 - 6.858)
0.165 - 0.180 (4.191 - 4.572)
0.045 - 0.055 (1.143 - 1.397)
0.460 - 0.500 (11.684 - 12.700)
0.570 - 0.620 (14.478 - 15.748) 0.330 - 0.370 (8.382 - 9.398) 0.700 - 0.728 (17.78 - 18.491)
0.620 (15.75) TYP
0.152 - 0.202 0.260 - 0.320 (3.861 - 5.131) (6.60 - 8.13)
0.095 - 0.115 (2.413 - 2.921)
0.013 - 0.023 (0.330 - 0.584) 0.057 - 0.077 (1.448 - 1.956) 0.028 - 0.038 (0.711 - 0.965) 0.135 - 0.165 (3.429 - 4.191) 0.155 - 0.195 (3.937 - 4.953)
T5 (TO-220) 0398
RELATED PARTS
PART NUMBER
LT1120A LTC 1174 LT1303 LT1376 LT1521
(R)
DESCRIPTION
125mA Low Dropout Regulator with 20A IQ High Efficiency 425mA Step-Down DC/DC Converter Micropower Step-Up DC/DC Converter 500kHz 1.25A Step-Down DC/DC Converter 300A Low Dropout Regulator with 15A IQ
COMMENTS
Includes 2.5V Reference and Comparator Over 90% Efficiency, Includes Comparator Includes Comparator, Good for EL Displays Uses Extremely Small External Components Lowest IQ Low Dropout Regulator
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
152935fa LT/TP 0499 2K REV A * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1995

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