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LT1763 Series 500mA, Low Noise, LDO Micropower Regulators
FEATURES
s s s s s s s s s s s
DESCRIPTIO
s s s s
Low Noise: 20VRMS (10Hz to 100kHz) Output Current: 500mA Low Quiescent Current: 30A Wide Input Voltage Range: 1.8V to 20V Low Dropout Voltage: 300mV Very Low Shutdown Current: < 1A No Protection Diodes Needed Fixed Output Voltages: 1.5V, 1.8V, 2.5V, 3V, 3.3V, 5V Adjustable Output from 1.22V to 20V Stable with 3.3F Output Capacitor Stable with Aluminum, Tantalum or Ceramic Capacitors Reverse Battery Protection No Reverse Current Overcurrent and Overtemperature Protected 8-Lead SO Package
APPLICATIO S
s s s
Cellular Phones Battery-Powered Systems Noise-Sensitive Instrumentation Systems
The LT (R)1763 series are micropower, low noise, low dropout regulators. The devices are capable of supplying 500mA of output current with a dropout voltage of 300mV. Designed for use in battery-powered systems, the low 30A quiescent current makes them an ideal choice. Quiescent current is well controlled; it does not rise in dropout as it does with many other regulators. A key feature of the LT1763 regulators is low output noise. With the addition of an external 0.01F bypass capacitor, output noise drops to 20VRMS over a 10Hz to 100kHz bandwidth. The LT1763 regulators are stable with output capacitors as low as 3.3F. Small ceramic capacitors can be used without the series resistance required by other regulators. Internal protection circuitry includes reverse battery protection, current limiting, thermal limiting and reverse current protection. The parts come in fixed output voltages of 1.5V, 1.8V, 2.5V, 3V, 3.3V and 5V, and as an adjustable device with a 1.22V reference voltage. The LT1763 regulators are available in the 8-lead SO package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
3.3V Low Noise Regulator
IN 1F OUT SENSE LT1763-3.3 SHDN BYP GND 0.01F
1763 TA01
400 350
VIN 3.7V TO 20V
+
3.3V AT 500mA 20VRMS NOISE 10F
DROPOUT VOLTAGE (mV)
300 250 200 150 100 50 0 0 100 300 400 200 OUTPUT CURRENT (mA) 500
1763 TA02
U
Dropout Voltage
U
U
1
LT1763 Series
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW OUT 1 SENSE/ADJ* 2 GND 3 BYP 4 8 7 6 5 IN GND GND SHDN
IN Pin Voltage ........................................................ 20V OUT Pin Voltage .................................................... 20V Input to Output Differential Voltage ....................... 20V SENSE Pin Voltage ............................................... 20V ADJ Pin Voltage ...................................................... 7V BYP Pin Voltage.................................................... 0.6V SHDN Pin Voltage ................................................. 20V Output Short-Circut Duration .......................... Indefinite Operating Junction Temperature Range (Note 2) ............................................ - 40C to 125C Storage Temperature Range ................. - 65C to 150C Lead Temperature (Soldering, 10 sec).................. 300C
ORDER PART NUMBER LT1763CS8 LT1763CS8-1.5 LT1763CS8-1.8 LT1763CS8-2.5 LT1763CS8-3 LT1763CS8-3.3 LT1763CS8-5 S8 PART MARKING 1763 17633 176315 176333 176318 17635 176325
S8 PACKAGE 8-LEAD PLASTIC SO
*PIN 2: SENSE FOR LT1763-2.5/ LT1763-3/LT1763-3.3/LT1763-5 ADJ FOR LT1763 TJMAX = 150C, JA = 70C/ W SEE THE APPLICATIONS INFORMATION SECTION.
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. (Note 2)
PARAMETER Minimum Operating Voltage Regulated Output Voltage (Note 4) CONDITIONS ILOAD = 500mA (Notes 3, 11) LT1763-1.5 VIN = 2V, ILOAD = 1mA 2.5V < VIN < 20V, 1mA < ILOAD < 500mA LT1763-1.8 VIN = 2.3V, ILOAD = 1mA 2.8V < VIN < 20V, 1mA < ILOAD < 500mA LT1763-2.5 VIN = 3V, ILOAD = 1mA 3.5V < VIN < 20V, 1mA < ILOAD < 500mA LT1763-3 VIN = 3.5V, ILOAD = 1mA 4V < VIN < 20V, 1mA < ILOAD < 500mA
q q q q q q q q q q q q q q q q
MIN 1.485 1.462 1.782 1.755 2.475 2.435 2.970 2.925 3.267 3.220 4.950 4.875 1.208 1.190
TYP 1.8 1.5 1.5 1.8 1.8 2.5 2.5 3 3 3.3 3.3 5 5 1.22 1.22 1 1 1 1 1 1 1 3 4
MAX 2.3 1.515 1.538 1.818 1.845 2.525 2.565 3.030 3.075 3.333 3.380 5.050 5.125 1.232 1.250 5 5 5 5 5 5 5 8 15 9 18 12 25
UNITS V V V V V V V V V V V V V V V mV mV mV mV mV mV mV mV mV mV mV mV mV
LT1763-3.3 VIN = 3.8V, ILOAD = 1mA 4.3V < VIN < 20V, 1mA < ILOAD < 500mA LT1763-5 ADJ Pin Voltage (Notes 3, 4) Line Regulation LT1763 VIN = 5.5V, ILOAD = 1mA 6V < VIN < 20V, 1mA < ILOAD < 500mA VIN = 2V, ILOAD = 1mA 2.22V < VIN < 20V, 1mA < ILOAD < 500mA VIN = 2V to 20V, ILOAD = 1mA VIN = 2.3V to 20V, ILOAD = 1mA VIN = 3V to 20V, ILOAD = 1mA VIN = 3.5V to 20V, ILOAD = 1mA VIN = 3.8V to 20V, ILOAD = 1mA VIN = 5.5V to 20V, ILOAD = 1mA VIN = 2V to 20V, ILOAD = 1mA VIN = 2.5V, ILOAD = 1mA to 500mA VIN = 2.5V, ILOAD = 1mA to 500mA VIN = 2.8V, ILOAD = 1mA to 500mA VIN = 2.8V, ILOAD = 1mA to 500mA VIN = 3.5V, ILOAD = 1mA to 500mA VIN = 3.5V, ILOAD = 1mA to 500mA
LT1763-1.5 LT1763-1.8 LT1763-2.5 LT1763-3 LT1763-3.3 LT1763-5 LT1763 (Note 3) LT1763-1.5 LT1763-1.8 LT1763-2.5
Load Regulation
q
5
q
2
U
W
U
U
WW
W
LT1763 Series
ELECTRICAL CHARACTERISTICS
The q denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25C. (Note 2)
PARAMETER Load Regulation CONDITIONS LT1763-3 LT1763-3.3 LT1763-5 LT1763 (Note 3) Dropout Voltage VIN = VOUT(NOMINAL) (Notes 5, 6, 11) ILOAD = 10mA ILOAD = 10mA ILOAD = 50mA ILOAD = 50mA ILOAD = 100mA ILOAD = 100mA ILOAD = 500mA ILOAD = 500mA GND Pin Current VIN = VOUT(NOMINAL) (Notes 5, 7) ILOAD = 0mA ILOAD = 1mA ILOAD = 50mA ILOAD = 100mA ILOAD = 250mA ILOAD = 500mA COUT = 10F, CBYP = 0.01F, ILOAD = 500mA, BW = 10Hz to 100kHz (Notes 3, 8) VOUT = Off to On VOUT = On to Off VSHDN = 0V VSHDN = 20V VIN = 6V, VSHDN = 0V VIN - VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz, ILOAD = 500mA VIN = 7V, VOUT = 0V VIN = VOUT(NOMINAL) + 1V, VOUT = - 0.1V VIN = - 20V, VOUT = 0V LT1763-1.5 LT1763-1.8 LT1763-2.5 LT1763-3 LT1763-3.3 LT1763-5 LT1763 (Note 3) VOUT = 1.5V, VIN < 1.5V VOUT = 1.8V, VIN < 1.8V VOUT = 2.5V, VIN < 2.5V VOUT = 3V, VIN < 3V VOUT = 3.3V, VIN < 3.3V VOUT = 5V, VIN < 5V VOUT = 1.22V, VIN < 1.22V
q q q q
MIN VIN = 4V, ILOAD = 1mA to 500mA VIN = 4V, ILOAD = 1mA to 500mA VIN = 4.3V, ILOAD = 1mA to 500mA VIN = 4.3V, ILOAD = 1mA to 500mA VIN = 6V, ILOAD = 1mA to 500mA VIN = 6V, ILOAD = 1mA to 500mA VIN = 2.3V, ILOAD = 1mA to 500mA VIN = 2.3V, ILOAD = 1mA to 500mA
q
TYP 7 7
MAX 15 30 17 33 25 50 6 12 0.19 0.25 0.22 0.32 0.24 0.34 0.35 0.45 75 120 1.6 3 8 16 100 2
UNITS mV mV mV mV mV mV mV mV V V V V V V V V A A mA mA mA mA VRMS nA V V A A
q
12
q
2
q
0.13
q
0.17
q
0.20
q
0.30
q q q q q q q
30 65 1.1 2 5 11 20 30 0.25 0.8 0.65 0.1 1 0.1 50 65 700 520
Output Voltage Noise ADJ Pin Bias Current Shutdown Threshold SHDN Pin Current (Note 9) Quiescent Current in Shutdown Ripple Rejection Current Limit Input Reverse Leakage Current Reverse Output Current (Note 10)
1
A dB mA mA
1 10 10 10 10 10 10 5 20 20 20 20 20 20 10
mA A A A A A A A
Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LT1763 regulators are tested and specified under pulse load conditions such that TJ TA. The LT1763 is 100% tested at TA = 25C. Performance at - 40C and 125C is assured by design, characterization and correlation with statistical process controls. Note 3: The LT1763 (adjustable version) is tested and specified for these conditions with the ADJ pin connected to the OUT pin. Note 4: Operating conditions are limited by maximum junction temperature. The regulated output voltage specification will not apply for
all possible combinations of input voltage and output current. When operating at maximum input voltage, the output current range must be limited. When operating at maximum output current, the input voltage range must be limited. Note 5: To satisfy requirements for minimum input voltage, the LT1763 (adjustable version) is tested and specified for these conditions with an external resistor divider (two 250k resistors) for an output voltage of 2.44V. The external resistor divider will add a 5A DC load on the output.
3
LT1763 Series
ELECTRICAL CHARACTERISTICS
Note 6: Dropout voltage is the minimum input to output voltage differential needed to maintain regulation at a specified output current. In dropout, the output voltage will be equal to: VIN - VDROPOUT. Note 7: GND pin current is tested with VIN = VOUT(NOMINAL) or VIN = 2.3V (whichever is greater) and a current source load. This means the device is tested while operating in its dropout region. This is the worst-case GND pin current. The GND pin current will decrease slightly at higher input voltages. Note 8: ADJ pin bias current flows into the ADJ pin. Note 9: SHDN pin current flows into the SHDN pin. Note 10: Reverse output current is tested with the IN pin grounded and the OUT pin forced to the rated output voltage. This current flows into the OUT pin and out the GND pin. Note 11: For the LT1763, LT1763-1.5 and LT1763-1.8 dropout voltage will be limited by the minimum input voltage specification under some output voltage/load conditions. See the curve of Minimum Input Voltage in the Typical Performance Characteristics.
TYPICAL PERFORMANCE CHARACTERISTICS
Typical Dropout Voltage
500 450
GUARANTEED DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
400 350 300 250 200 150 100 50 0 0
50 100 150 200 250 300 350 400 450 500 OUTPUT CURRENT (mA)
1763 G01
Quiescent Current
50 45
QUIESCENT CURRENT (A)
DROPOUT VOLTAGE (mV)
40 35 30 25 20 15 10 5 VIN = 6V RL = , IL = 0 (LT1763-2.5/-3/-3.3/-5) RL = 250k, IL = 5A (LT1763) 0 25 50 75 100 125 VSHDN = VIN
0 -50 -25
TEMPERATURE (C)
1763 G04
4
UW
TJ = 125C
Guaranteed Dropout Voltage
500 450 400 350 300 250 200 150 100 50 0 0 50 100 150 200 250 300 350 400 450 500 OUTPUT CURRENT (mA)
1763 G02
= TEST POINTS
TJ 125C TJ 25C
TJ = 25C
Dropout Voltage
500 450 400 350 300 250 200 150 100 50 0 -50 -25 50 25 0 75 TEMPERATURE (C) 100 125 IL = 100mA IL = 50mA IL = 10mA IL = 1mA IL = 500mA IL = 250mA
1763 G03
LT1763 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1763-2.5 Output Voltage
2.54 IL = 1mA 2.53 3.045 2.52 2.51 2.50 2.49 2.48 2.47 2.46 -50 -25 0 25 50 75 100 125 3.030 3.015 3.000 2.985 2.970 2.955 2.940 -50 -25 0 25 50 75 100 125 3.060 IL = 1mA 3.345
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
TEMPERATURE (C)
1763 G05
LT1763-5 Output Voltage
5.100 IL = 1mA 5.075
OUTPUT VOLTAGE (V) ADJ PIN VOLTAGE (V)
5.050 5.025 5.000 4.975 4.950 4.925 4.900 -50 -25 0 25 50 75 100 125
1.230 1.225 1.220 1.215 1.210 1.205 1.200 -50 -25 0 25 50 75 100 125
QUIESCENT CURRENT (A)
TEMPERATURE (C)
1763 G08
LT1763-3 Quiescent Current
250 225 TJ = 25C RL =
QUIESCENT CURRENT (A)
QUIESCENT CURRENT (A)
175 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10
175 150 125 100 75 50 25 0 0 1 2 VSHDN = VIN VSHDN = 0V 34567 INPUT VOLTAGE (V) 8 9 10
QUIESCENT CURRENT (A)
200
UW
1763 G11
LT1763-3 Output Voltage
3.360
LT1763-3.3 Output Voltage
IL = 1mA 3.330 3.315 3.300 3.285 3.270 3.255 3.240 -50 -25 0 25 50 75 100 125
TEMPERATURE (C)
1763 G06
TEMPERATURE (C)
1763 G07
LT1763 ADJ Pin Voltage
1.240 1.235 IL = 1mA 250 225 200 175 150 125 100 75 50 25 0
LT1763-2.5 Quiescent Current
TJ = 25C RL =
VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
TEMPERATURE (C)
1763 G09
1763 G10
LT1763-3.3 Quiescent Current
250 225 200 TJ = 25C RL = 250 225 200 175 150 125 100 75 50 25 0
LT1763-5 Quiescent Current
TJ = 25C RL =
VSHDN = VIN VSHDN = 0V 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1763 G12
1763 G13
5
LT1763 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1763 Quiescent Current
40 35 TJ = 25C RL = 250k 1200 1000
QUIESCENT CURRENT (A)
GND PIN CURRENT (A)
25 20 15 10 5 0 0 2 4 VSHDN = 0V 6 8 10 12 14 16 18 20 INPUT VOLTAGE (V)
1763 G14
800 600 400 200 0
GND PIN CURRENT (A)
30
VSHDN = VIN
LT1763-3.3 GND Pin Current
1200 1000
GND PIN CURRENT (A)
GND PIN CURRENT (A)
800 600 400 200 0 RL = 330 IL = 10mA* RL = 3.3k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 TJ = 25C VIN = VSHDN *FOR VOUT = 3.3V
800 600 400 200 0
GND PIN CURRENT (A)
RL = 66 IL = 50mA*
LT1763-2.5 GND Pin Current
12 10 TJ = 25C VIN = VSHDN *FOR VOUT = 2.5V RL = 5 IL = 500mA* RL = 8.33 IL = 300mA* RL = 25 IL = 100mA*
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
8 6 4 2 0
0
1
2
34567 INPUT VOLTAGE (V)
6
UW
1763 G17
LT1763-2.5 GND Pin Current
1200 1000 RL = 50 IL = 50mA* TJ = 25C VIN = VSHDN *FOR VOUT = 2.5V RL = 250 IL = 10mA* RL = 2.5k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 800 600 400 200 0
LT1763-3 GND Pin Current
RL = 60 IL = 50mA* TJ = 25C VIN = VSHDN *FOR VOUT = 3V RL = 300 IL = 10mA* RL = 3k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1763 G15
1763 G16
LT1763-5 GND Pin Current
1200 1000 RL = 100 IL = 50mA* TJ = 25C VIN = VSHDN *FOR VOUT = 5V RL = 500 IL = 10mA* RL = 5k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10 1200 1000 800 600 400 200 0
LT1763 GND Pin Current
RL = 24.4 IL = 50mA* TJ = 25C VIN = VSHDN *FOR VOUT = 1.22V RL = 122 IL = 10mA* RL = 1.22k IL = 1mA* 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
1763 G18
1763 G19
LT1763-3 GND Pin Current
12 10 8 6 4 2 0 RL = 30 IL = 100mA* RL = 6 IL = 500mA* RL = 10 IL = 300mA* TJ = 25C VIN = VSHDN *FOR VOUT = 3V 12 10 8 6 4 2 0 0 1 2 34567 INPUT VOLTAGE (V) 8 9 10
LT1763-3.3 GND Pin Current
TJ = 25C VIN = VSHDN *FOR VOUT = 3.3V RL = 6.6 IL = 500mA* RL = 11 IL = 300mA* RL = 33 IL = 100mA*
8
9
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
1763 G20
1763 G21
1763 G22
LT1763 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1763-5 GND Pin Current
12 10 TJ = 25C VIN = VSHDN *FOR VOUT = 5V RL = 10 IL = 500mA* 12 10 TJ = 25C VIN = VSHDN *FOR VOUT = 1.22V RL = 2.44 IL = 500mA* RL = 4.07 IL = 300mA*
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
8 6 4 2 0 RL = 50 IL = 100mA* RL = 16.7 IL = 300mA*
8 6 4 2 0
GND PIN CURRENT (mA)
0
1
2
34567 INPUT VOLTAGE (V)
SHDN Pin Threshold (On-to-Off)
1.0 0.9
SHDN PIN THRESHOLD (V)
1.0
IL = 1mA
SHDN PIN THRESHOLD (V)
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -50 -25 50 0 75 25 TEMPERATURE (C) 100 125
0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 -50 -25 50 0 75 25 TEMPERATURE (C) 100 125 IL = 1mA IL = 500mA
SHDN PIN INPUT CURRENT (A)
SHDN Pin Input Current
1.6 VSHDN = 20V
SHDN PIN INPUT CURRENT (A)
140 120 ADJ PIN BIAS CURRENT (nA)
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 -50 -25 0 25 50 75 100 125
CURRENT LIMIT (A)
TEMPERATURE (C)
1763 G29
UW
8 9
1763 G23
LT1763 GND Pin Current
12
GND Pin Current vs ILOAD
VIN = VOUT(NOMINAL) + 1V 10 8 6 4 2 0
RL = 12.2 IL = 100mA*
10
0
1
2
34567 INPUT VOLTAGE (V)
8
9
10
0
50 100 150 200 250 300 350 400 450 500 OUTPUT CURRENT (mA)
1763 G25
1763 G24
SHDN Pin Threshold (Off-to-On)
1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0.9
SHDN Pin Input Current
0
1
2
345678 SHDN PIN VOLTAGE (V)
9
10
1763 G26
1763 G27
1763 G28
ADJ Pin Bias Current
1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2
Current Limit
VOUT = 0V
100 80 60 40 20 0 -50 -25
0.1 0
50 25 0 75 TEMPERATURE (C)
100
125
0
1
4 3 2 5 INPUT VOLTAGE (V)
6
7
1763 G31
1763 G30
7
LT1763 Series TYPICAL PERFORMANCE CHARACTERISTICS
Current Limit
1.2 1.0
CURRENT LIMIT (A)
REVERSE OUTPUT CURRENT (A)
REVERSE OUTPUT CURRENT (A)
VIN = 7 VOUT = 0V
0.8 0.6 0.4 0.2 0 -50 -25
50 25 0 75 TEMPERATURE (C)
Input Ripple Rejection
80 70 80
RIPPLE REJECTION (dB)
RIPPLE REJECTION (dB)
50 40 30 20 10 0 10 100 IL = 500mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE CBYP = 0
COUT = 10F
50 CBYP = 1000pF 40 30 20 10 0 IL = 500mA VIN = VOUT(NOMINAL) + 1V + 50mVRMS RIPPLE COUT = 10F 10 100 1k 10k FREQUENCY (Hz) 100k 1M
1763 G36
RIPPLE REJECTION (dB)
60
COUT = 4.7F
1k 10k FREQUENCY (Hz)
100k
LT1763 Minimum Input Voltage
2.50 2.25 MINIMUM INPUT VOLTAGE (V) IL = 500mA
5
LT1763 0
LT1763-2.5
1.75 1.50 1.25 1.00 0.75 0.50 0.25 VOUT = 1.22V 50 25 0 75 TEMPERATURE (C) 100 125 IL = 1mA
LOAD REGULATION (mV)
2.00
OUTPUT NOISE SPECTRAL DENSITY (V/Hz)
0 -50 -25
8
UW
100
1763 G32
Reverse Output Current
100 90 80 70 60 50 40 30 20 10 0 125 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10 LT1763-5 LT1763 LT1763-2.5 LT1763-3 LT1763-3.3 TJ = 25C, VIN = 0V CURRENT FLOWS INTO OUTPUT PIN VOUT = VADJ (LT1763)
20 18 16 14 12 10 8 6 4 2
Reverse Output Current
VIN = 0V VOUT = 1.22V (LT1763) VOUT = 2.5V (LT1763-2.5) VOUT = 3V (LT1763-3) VOUT = 3.3V (LT1763-3.3) VOUT = 5V (LT1763-5)
LT1763-2.5/-3/-3.3/-5
LT1763
0 -50 -25
50 25 0 75 TEMPERATURE (C)
100
125
1763 G33
1763 G34
Input Ripple Rejection
68 66 64 62 60 58 56 54
70 CBYP = 0.01F 60
Ripple Rejection
CBYP = 100pF
VIN = VOUT (NOMINAL) + 1V + 0.5VP-P RIPPLE AT f = 120Hz IL = 500mA 0 25 50 75 100 125
1M
1763 G35
52 -50 -25
TEMPERATURE (C)
1763 G37
Load Regulation
10
Output Noise Spectral Density CBYP = 0
LT1763-5 1 LT1763-2.5 LT1763 0.1
LT1763-3.3
-5 -10 -15 -20 LT1763-3 LT1763-3.3 LT1763-5
LT1763-3
VIN = VOUT(NOMINAL) + 1V IL = 1mA TO 500mA 0 25 50 75 100 125
COUT = 10F IL = 500mA 0.01 10 100 1k 10k FREQUENCY (Hz) 100k
1763 G40
-25 -50 -25
TEMPERATURE (C)
1763 G38
1763 G39
LT1763 Series TYPICAL PERFORMANCE CHARACTERISTICS
Output Noise Spectral Density
OUTPUT NOISE SPECTRAL DENSITY (V/Hz)
10 COUT = 10F IL = 500mA
OUTPUT NOISE (VRMS)
OUTPUT NOISE (VRMS)
LT1763-5 1 LT1763
CBYP = 1000pF CBYP = 100pF
0.1
CBYP = 0.01F
0.01 10
100
1k 10k FREQUENCY (Hz)
LT1763-5 10Hz to 100kHz Output Noise CBYP = 0
VOUT 100V/DIV
COUT = 10F IL = 500mA
LT1763-5 10Hz to 100kHz Output Noise CBYP = 1000pF
VOUT 100V/DIV
1ms/DIV COUT = 10F IL = 500mA COUT = 10F IL = 500mA
UW
1763 G41
RMS Output Noise vs Bypass Capacitor
160 140 120 100 80 60 40 20 0
100k
RMS Output Noise vs Load Current (10Hz to 100kHz)
160 140 120 LT1763-5 100 80 60 40 20 1000 10000
1763 G42
COUT = 10F IL = 500mA f = 10Hz TO 100kHz LT1763-5 LT1763-3.3 LT1763-3
COUT = 10F CBYP = 0 CBYP = 0.01F
LT1763 LT1763-2.5
LT1763
LT1763-5 LT1763
10
100 CBYP (pF)
0 0.01
0.1
10 100 1 LOAD CURRENT (mA)
1000
1763 G43
LT1763-5 10Hz to 100kHz Output Noise CBYP = 100pF
VOUT 100V/DIV
1ms/DIV
1763 G46
LT1763-5 10Hz to 100kHz Output Noise CBYP = 0.01F
VOUT 100V/DIV
1ms/DIV
1763 G47 1763 G44
1ms/DIV COUT = 10F IL = 500mA
1763 G45
9
LT1763 Series TYPICAL PERFORMANCE CHARACTERISTICS
LT1763-5 Transient Response CBYP = 0
OUTPUT VOLTAGE DEVIATION (V)
0.2 0 -0.2 -0.4
OUTPUT VOLTAGE DEVIATION (V)
0.4
VIN = 6V CIN = 10F COUT = 10F
LOAD CURRENT (mA)
600 400 200 0 0 200 400 600 TIME (s) 800 1000
1763 G48
LOAD CURRENT (mA)
PIN FUNCTIONS
OUT (Pin 1): Output. The output supplies power to the load. A minimum output capacitor of 3.3F is required to prevent oscillations. Larger output capacitors will be required for applications with large transient loads to limit peak voltage transients. See the Applications Information section for more information on output capacitance and reverse output characteristics. SENSE (Pin 2): Output Sense. For fixed voltage versions of the LT1763 (LT1763-2.5/LT1763-3/LT1763-3.3/ LT1763-5), the SENSE pin is the input to the error amplifier. Optimum regulation will be obtained at the point where the SENSE pin is connected to the OUT pin of the regulator. In critical applications, small voltage drops are caused by the resistance (RP) of PC traces between the regulator and the load. These may be eliminated by connecting the SENSE pin to the output at the load as shown in Figure 1 (Kelvin Sense Connection). Note that the voltage drop across the external PC traces will add to the dropout voltage of the regulator. The SENSE pin bias current is 10A at the nominal rated output voltage. The SENSE pin can be pulled below ground (as in a dual supply system where the regulator load is returned to a negative supply) and still allow the device to start and operate. ADJ (Pin 2): Adjust. For the adjustable LT1763, this is the input to the error amplifier. This pin is internally clamped to 7V. It has a bias current of 30nA which flows into the pin (see curve of ADJ Pin Bias Current vs Temperature in the Typical Performance Characteristics section). The ADJ pin voltage is 1.22V referenced to ground and the output voltage range is 1.22V to 20V. BYP (Pin 4): Bypass. The BYP pin is used to bypass the reference of the LT1763 regulators to achieve low noise performance from the regulator. The BYP pin is clamped internally to 0.6V (one VBE). A small capacitor from the output to this pin will bypass the reference to lower the output voltage noise. A maximum value of 0.01F can be
8 IN LT1763 OUT 1 RP
10
UW
LT1763-5 Transient Response CBYP = 0.01F
0.10 0.05 0 -0.05 -0.10 VIN = 6V CIN = 10F COUT = 10F
600 400 200 0 0 10 20 30 40 50 60 70 80 90 100 TIME (s)
1763 G49
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+
VIN
5
SHDN
SENSE GND 3
2
+
LOAD
RP
1763 F01
Figure 1. Kelvin Sense Connection
LT1763 Series
PIN FUNCTIONS
used for reducing output voltage noise to a typical 20VRMS over a 10Hz to 100kHz bandwidth. If not used, this pin must be left unconnected. GND (Pins 3, 6, 7): Ground. SHDN (Pin 5): Shutdown. The SHDN pin is used to put the LT1763 regulators into a low power shutdown state. The output will be off when the SHDN pin is pulled low. The SHDN pin can be driven either by 5V logic or opencollector logic with a pull-up resistor. The pull-up resistor is required to supply the pull-up current of the opencollector gate, normally several microamperes, and the SHDN pin current, typically 1A. If unused, the SHDN pin must be connected to VIN. The device will be in the low power shutdown state if the SHDN pin is not connected. IN (Pin 8): Input. Power is supplied to the device through the IN pin. A bypass capacitor is required on this pin if the device is more than six inches away from the main input filter capacitor. In general, the output impedance of a battery rises with frequency, so it is advisable to include a bypass capacitor in battery-powered circuits. A bypass capacitor in the range of 1F to 10F is sufficient. The LT1763 regulators are designed to withstand reverse voltages on the IN pin with respect to ground and the OUT pin. In the case of a reverse input, which can happen if a battery is plugged in backwards, the device will act as if there is a diode in series with its input. There will be no reverse current flow into the regulator and no reverse voltage will appear at the load. The device will protect both itself and the load.
APPLICATIONS INFORMATION
The LT1763 series are 500mA low dropout regulators with micropower quiescent current and shutdown. The devices are capable of supplying 500mA at a dropout voltage of 300mV. Output voltage noise can be lowered to 20VRMS over a 10Hz to 100kHz bandwidth with the addition of a 0.01F reference bypass capacitor. Additionally, the reference bypass capacitor will improve transient response of the regulator, lowering the settling time for transient load conditions. The low operating quiescent current (30A) drops to less than 1A in shutdown. In addition to the low quiescent current, the LT1763 regulators incorporate several protection features which make them ideal for use in battery-powered systems. The devices are protected against both reverse input and reverse output voltages. In battery backup applications where the output can be held up by a backup battery when the input is pulled to ground, the LT1763-X acts like it has a diode in series with its output and prevents reverse current flow. Additionally, in dual supply applications where the regulator load is returned to a negative supply, the output can be pulled below ground by as much as 20V and still allow the device to start and operate. Adjustable Operation The adjustable version of the LT1763 has an output voltage range of 1.22V to 20V. The output voltage is set by the ratio of two external resistors as shown in Figure 2. The device servos the output to maintain the ADJ pin voltage at 1.22V referenced to ground. The current in R1 is then equal to 1.22V/R1 and the current in R2 is the current in R1 plus the ADJ pin bias current. The ADJ pin bias current, 30nA at 25C, flows through R2 into the ADJ pin. The output voltage can be calculated using the formula in Figure 2. The value of R1 should be no greater than 250k to minimize errors in the output voltage caused by the ADJ pin bias current. Note that in shutdown the output is turned off and the divider current will be zero. Curves of ADJ Pin Voltage vs Temperature and ADJ Pin Bias Current vs Temperature appear in the Typical Performance Characteristics section. The adjustable device is tested and specified with the ADJ pin tied to the OUT pin for an output voltage of 1.22V. Specifications for output voltages greater than 1.22V will
IN VIN LT1763 ADJ GND R1
1763 F02
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OUT
VOUT
+
R2
R2 VOUT = 1.22V 1 + + (IADJ )(R2) R1 VADJ = 1.22V IADJ = 30nA AT 25C OUTPUT RANGE = 1.22V TO 20V
Figure 2. Adjustable Operation
11
LT1763 Series
APPLICATIONS INFORMATION
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 500mA is - 2mV typical at VOUT = 1.22V. At VOUT = 12V, load regulation is: (12V/1.22V)(-2mV) = - 19.6mV Bypass Capacitance and Low Noise Performance The LT1763 regulators may be used with the addition of a bypass capacitor from VOUT to the BYP pin to lower output voltage noise. A good quality low leakage capacitor is recommended. This capacitor will bypass the reference of the regulator, providing a low frequency noise pole. The noise pole provided by this bypass capacitor will lower the output voltage noise to as low as 20VRMS with the addition of a 0.01F bypass capacitor. Using a bypass capacitor has the added benefit of improving transient response. With no bypass capacitor and a 10F output capacitor, a 10mA to 500mA 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 settle to within 1% for a 10mA to 500mA load step in less than 10s, with total output voltage deviation of less than 2.5% (see LT1763-5 Transient Response in the Typical Performance Characteristics). However, regulator start-up time is inversely proportional to the size of the bypass capacitor, slowing to 15ms with a 0.01F bypass capacitor and 10F output capacitor. Output Capacitance and Transient Response The LT1763 regulators are designed to be stable with a wide range of output capacitors. The ESR of the output capacitor affects stability, most notably with small capacitors. A minimum output capacitor of 3.3F with an ESR of 3 or less is recommended to prevent oscillations. The LT1763-X is a micropower device and output transient response will be a function of output capacitance. Larger values of output capacitance decrease the peak deviations and provide improved transient response for larger load current changes. Bypass capacitors, used to decouple individual components powered by the LT1763-X, will increase the effective output capacitor value. With larger capacitors used to bypass the reference (for low noise operation), larger values of output capacitors are needed. For 100pF of bypass capacitance, 4.7F of output capacitor is recommended. With a 1000pF bypass capacitor or larger, a 6.8F output capacitor is recommended. The shaded region of Figure 3 defines the range over which the LT1763 regulators are stable. The minimum ESR needed is defined by the amount of bypass capacitance used, while the maximum ESR is 3. Extra consideration must be given to the use of ceramic capacitors. Ceramic capacitors are manufactured with a variety of dielectrics, each with different behavior across temperature and applied voltage. The most common dielectrics used are Z5U, Y5V, X5R and X7R. The Z5U and Y5V dielectrics are good for providing high capacitances in a small package, but exhibit strong voltage and temperature coefficients as shown in Figures 4 and 5. When used with a 5V regulator, a 10F Y5V capacitor can exhibit an effective value as low as 1F to 2F over the operating temperature range. The X5R and X7R dielectrics result in more stable characteristics and are more suitable for use as the output capacitor. The X7R type has better stability across temperature, while the X5R is less expensive and is available in higher values. Voltage and temperature coefficients are not the only sources of problems. Some ceramic capacitors have a piezoelectric response. A piezoelectric device generates voltage across its terminals due to mechanical stress, similar to the way a piezoelectric accelerometer or microphone works. For a ceramic capacitor the stress can be
4.0 3.5 3.0 STABLE REGION 2.5
ESR ()
12
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2.0 1.5 1.0 0.5 0 1 3 2 4 5 6 7 8 9 10 OUTPUT CAPACITANCE (F)
1763 F03
CBYP = 0 CBYP = 100pF CBYP = 330pF CBYP 1000pF
Figure 3. Stability
LT1763 Series
APPLICATIONS INFORMATION
20 0 BOTH CAPACITORS ARE 16V, 1210 CASE SIZE, 10F X5R -20 -40 -60 Y5V -80 -100
CHANGE IN VALUE (%)
0
2
4
8 6 10 12 DC BIAS VOLTAGE (V)
14
16
1763 F04
Figure 4. 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) Y5V
X5R
-100 -50 -25
100
125
1763 F05
Figure 5. Ceramic Capacitor Temperature Characteristics
LT1763-5 COUT = 10F CBYP = 0.01f ILOAD = 100mA VOUT 500V/DIV
100ms/DIV
1763 F06
Figure 6. Noise Resulting from Tapping on a Ceramic Capacitor
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induced by vibrations in the system or thermal transients. The resulting voltages produced can cause appreciable amounts of noise, especially when a ceramic capacitor is used for noise bypassing. A ceramic capacitor produced Figure 6's trace in response to light tapping from a pencil. Similar vibration induced behavior can masquerade as increased output voltage noise. Thermal Considerations The power handling capability of the device will be limited by the maximum rated junction temperature (125C). The power dissipated by the device will be made up of two components: 1. Output current multiplied by the input/output voltage differential: (IOUT)(VIN - VOUT), and 2. GND pin current multiplied by the input voltage: (IGND)(VIN). 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 LT1763 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions, the maximum junction temperature rating of 125C must not be exceeded. It is important to give careful consideration to all sources of thermal resistance from junction to ambient. Additional heat sources mounted nearby must also be considered. For surface mount devices, heat sinking is accomplished by using the heat spreading capabilities of the PC board and its copper traces. Copper board stiffeners and plated through-holes can also be used to spread the heat generated by power devices. The following table lists thermal resistance for several different board sizes and copper areas. All measurements were taken in still air on 3/32" FR-4 board with one ounce copper.
13
LT1763 Series
APPLICATIONS INFORMATION
Table 1. Measured Thermal Resistance
COPPER AREA TOPSIDE* 2500mm 1000mm
2 2
THERMAL RESISTANCE BOARD AREA 2500mm 2500mm
2 2
BACKSIDE 2500mm 2500mm
2 2
(JUNCTION-TO-AMBIENT) 60C/W 60C/W 68C/W 74C/W 86C/W
225mm2 100mm 50mm
2 2
2500mm2 2500mm 2500mm
2 2
2500mm2 2500mm 2500mm
2 2
*Device is mounted on topside.
Calculating Junction Temperature Example: Given an output voltage of 3.3V, an input voltage range of 4V to 6V, an output current range of 0mA to 250mA 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) = 250mA VIN(MAX) = 6V IGND at (IOUT = 250mA, VIN = 6V) = 5mA So, P = 250mA(6V - 3.3V) + 5mA(6V) = 0.71W The thermal resistance will be in the range of 60C/W to 86C/W depending on the copper area. So the junction temperature rise above ambient will be approximately equal to: 0.71W(75C/W) = 53.3C The maximum junction temperature will then be equal to the maximum junction temperature rise above ambient plus the maximum ambient temperature or: TJMAX = 50C + 53.3C = 103.3C Protection Features The LT1763 regulators incorporate several protection features which make them ideal for use in battery-powered circuits. In addition to the normal protection features associated with monolithic regulators, such as current
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limiting and thermal limiting, the devices are protected against reverse input voltages, reverse output voltages and reverse voltages from output to input. Current limit protection and thermal overload protection are intended to protect the device against current overload conditions at the output of the device. For normal operation, the junction temperature should not exceed 125C. The input of the device will withstand reverse voltages of 20V. Current flow into the device will be limited to less than 1mA (typically less than 100A) and no negative voltage will appear at the output. The device will protect both itself and the load. This provides protection against batteries which can be plugged in backward. The output of the LT1763-X can be pulled below ground without damaging the device. If the input is left open circuit or grounded, the output can be pulled below ground by 20V. For fixed voltage versions, the output will act like a large resistor, typically 500k or higher, limiting current flow to less than 100A. For adjustable versions, the output will act like an open circuit; no current will flow out of the pin. If the input is powered by a voltage source, the output will source the short-circuit current of the device and will protect itself by thermal limiting. In this case, grounding the SHDN pin will turn off the device and stop the output from sourcing the short-circuit current. The ADJ pin of the adjustable device can be pulled above or below ground by as much as 7V without damaging the device. If the input is left open circuit or grounded, the ADJ pin will act like an open circuit when pulled below ground and like a large resistor (typically 100k) in series with a diode when pulled above ground. In situations where the ADJ pin is connected to a resistor divider that would pull the ADJ pin above its 7V clamp voltage if the output is pulled high, the ADJ pin input current must be limited to less than 5mA. For example, a resistor divider is used to provide a regulated 1.5V output from the 1.22V reference when the output is forced to 20V. The top resistor of the resistor divider must be chosen to limit the current into the ADJ pin to less than 5mA when the ADJ pin is at 7V. The 13V difference between output and ADJ pin divided by the 5mA maximum current into the ADJ pin yields a minimum top resistor value of 2.6k.
LT1763 Series
APPLICATIONS INFORMATION
REVERSE OUTPUT CURRENT (A)
In circuits where a backup battery is required, several different input/output conditions can occur. The output voltage may be held up while the input is either pulled to ground, pulled to some intermediate voltage or is left open circuit. Current flow back into the output will follow the curve shown in Figure 7. When the IN pin of the LT1763-X is forced below the OUT pin or the OUT pin is pulled above the IN pin, input current will typically drop to less than 2A. This can happen if the input of the device is connected to a discharged (low voltage) battery and the output is held up by either a backup battery or a second regulator circuit. The state of the SHDN pin will have no effect on the reverse output current when the output is pulled above the input.
PACKAGE DESCRIPTION
Dimensions in inches (millimeters) unless otherwise noted.
S8 Package 8-Lead Plastic Small Outline (Narrow 0.150)
(LTC DWG # 05-08-1610)
0.010 - 0.020 x 45 (0.254 - 0.508) 0.008 - 0.010 (0.203 - 0.254) 0- 8 TYP
0.014 - 0.019 (0.355 - 0.483) TYP *DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE
0.016 - 0.050 (0.406 - 1.270)
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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100 90 80 70 60 50 40 30 20 10 0 0 1 2 345678 OUTPUT VOLTAGE (V) 9 10 LT1763-5 LT1763-3.3 LT1763-3 LT1763-2.5 TJ = 25C VIN = 0V CURRENT FLOWS INTO OUTPUT PIN VOUT = VADJ (LT1763) LT1763
1763 F07
Figure 7. Reverse Output Current
0.189 - 0.197* (4.801 - 5.004) 8 7 6 5
0.228 - 0.244 (5.791 - 6.197)
0.150 - 0.157** (3.810 - 3.988)
1
2
3
4
0.053 - 0.069 (1.346 - 1.752)
0.004 - 0.010 (0.101 - 0.254)
0.050 (1.270) BSC
SO8 1298
15
LT1763 Series
TYPICAL APPLICATION
Paralleling of Regulators for Higher Output Current
R1 0.1
+
VIN > 3.8V
RELATED PARTS
PART NUMBER LT1120 LT1121 LT1129 LT1175 LT1521 LT1529 LT1611 LT1613 LTC1627 LT1761 Series LT1762 Series LT1764 Series DESCRIPTION 125mA Low Dropout Regulator with 20A IQ 150mA Micropower Low Dropout Regulator 700mA Micropower Low Dropout Regulator 500mA Negative Low Dropout Micropower Regulator 300mA Low Dropout Micropower Regulator with Shutdown 3A Low Dropout Regulator with 50A IQ Inverting 1.4MHz Switching Regulator 1.4MHz Single-Cell Micropower DC/DC Converter High Efficiency Synchronous Step-Down Switching Regulator 100mA, Low Noise, Low Dropout Micropower Regulators in SOT-23 150mA, Low Noise, LDO Micropower Regulators 3A, Fast Transient Response Low Dropout Regulator COMMENTS Includes 2.5V Reference and Comparator 30A IQ, SOT-223 Package 50A Quiescent Current 45A IQ, 0.26V Dropout Voltage, SOT-223 Package 15A IQ, Reverse Battery Protection 500mV Dropout Voltage 5V to - 5V at 150mA, Low Output Noise, SOT-23 Package SOT-23 Package, Internally Compensated Burst ModeTM Operation, Monolithic, 100% Duty Cycle 20A Quiescent Current, 20VRMS Noise 25A Quiescent Current, 20VRMS Noise 340mV Dropout Voltage
Burst Mode is a trademark of Linear Technology Corporation.
16
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 q FAX: (408) 434-0507 q www.linear-tech.com
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IN C1 10F
OUT FB LT1763-3.3 C4 0.01F
+
3.3V 1A C2 10F
SHDN BYP GND R2 0.1 IN LT1763 BYP SHDN SHDN ADJ GND OUT C5 0.01F R6 2k
R7 1.21k
R3 2.2k
R4 2.2k
3
+ -
8 1
R5 10k
1/2 LT1490 2 4
1763 TA03
C3 0.01F
1763FS sn1763 LT/TP 0899 4K * PRINTED IN USA
(c) LINEAR TECHNOLOGY CORPORATION 1999

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