LINER LT1761ES5-2 100ma, low noise, ldo micropower regulators in sot-23 Datasheet

LT1761 Series
100mA, Low Noise,
LDO Micropower
Regulators in SOT-23
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FEATURES
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DESCRIPTIO
Tiny 5-Lead SOT-23 Package
Low Noise: 20µVRMS (10Hz to 100kHz)
Low Quiescent Current: 20µA
Wide Input Voltage Range: 1.8V to 20V
Output Current: 100mA
Very Low Shutdown Current: < 0.1µA
Low Dropout Voltage: 300mV at 100mA
Fixed Output Voltages: 1.5V, 1.8V, 2V, 2.5V, 2.8V,
3V, 3.3V, 5V
Adjustable Output from 1.22V to 20V
Stable with 1µF Output Capacitor
Stable with Aluminum, Tantalum or
Ceramic Capacitors
Reverse Battery Protected
No Reverse Current
No Protection Diodes Needed
Overcurrent and Overtemperature Protected
The LT ®1761 series are micropower, low noise, low
dropout regulators. With an external 0.01µF bypass
capacitor, output noise drops to 20µVRMS over a 10Hz to
100kHz bandwidth. Designed for use in battery-powered
systems, the low 20µA quiescent current makes them an
ideal choice. In shutdown, quiescent current drops to less
than 0.1µA. The devices are capable of operating over an
input voltage from 1.8V to 20V, and can supply 100mA of
output current with a dropout voltage of 300mV. Quiescent current is well controlled, not rising in dropout as it
does with many other regulators.
The LT1761 regulators are stable with output capacitors
as low as 1µF. 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 device is available in fixed output
voltages of 1.5V, 1.8V, 2V, 2.5V, 2.8V, 3V, 3.3V and 5V,
and as an adjustable device with a 1.22V reference voltage.
The LT1761 regulators are available in the 5-lead SOT-23
package.
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APPLICATIO S
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Cellular Phones
Pagers
Battery-Powered Systems
Frequency Synthesizers
Wireless Modems
, LTC and LT are registered trademarks of Linear Technology Corporation.
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TYPICAL APPLICATIO
10Hz to 100kHz Output Noise
5V Low Noise Regulator
VIN
5.4V TO
20V
IN
1µF
OUT
LT1761-5
SHDN
GND
0.01µF
+
5V AT100mA
20µVRMS NOISE
10µF
BYP
VOUT
100µV/DIV
20µVRMS
1761 TA01
1761 G48
1
LT1761 Series
W W
W
AXI U
U
ABSOLUTE
RATI GS
(Note 1)
IN Pin Voltage ........................................................ ±20V
OUT Pin Voltage .................................................... ±20V
Input to Output Differential 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) ............................................ – 40°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
U
U
W
PACKAGE/ORDER I FOR ATIO
TOP VIEW
IN 1
TOP VIEW
5 OUT
GND 2
BYP 3
IN 1
TOP VIEW
5 OUT
4 ADJ
SHDN 3
S5 PACKAGE
5-LEAD PLASTIC SOT-23
5 OUT
IN 1
GND 2
GND 2
4 ADJ
SHDN 3
S5 PACKAGE
5-LEAD PLASTIC SOT-23
4 BYP
TJMAX = 150°C, θJA = 250°C/ W
TJMAX = 150°C, θJA = 250°C/ W
S5 PACKAGE
5-LEAD PLASTIC SOT-23
TJMAX = 150°C, θJA = 250°C/ W
SEE THE APPLICATIONS INFORMATION SECTION.
SEE THE APPLICATIONS INFORMATION SECTION.
SEE THE APPLICATIONS INFORMATION SECTION.
ORDER PART
NUMBER
S5 PART
MARKING
ORDER PART
NUMBER
S5 PART
MARKING
ORDER PART
NUMBER
S5 PART
MARKING
LT1761ES5-BYP
LTGC
LT1761ES5-SD
LTGH
LT1761ES5-1.5
LT1761ES5-1.8
LT1761ES5-2
LT1761ES5-2.5
LT1761ES5-2.8
LT1761ES5-3
LT1761ES5-3.3
LT1761ES5-5
LTMT
LTJM
LTJE
LTGD
LTLB
LTGE
LTGF
LTGG
Consult factory for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2)
PARAMETER
CONDITIONS
MIN
Minimum Input Voltage (Notes 3, 11) ILOAD = 100mA
Regulated Output Voltage
LT1761-1.5
VIN = 2V, ILOAD = 1mA
(Note 4)
2.5V < VIN < 20V, 1mA < ILOAD < 50mA
2.5V < VIN < 20V, 1mA < ILOAD < 100mA
LT1761-1.8
LT1761-2
LT1761-2.5
2
●
TYP
MAX
UNITS
1.8
2.3
V
●
●
1.478
1.457
1.436
1.5
1.5
1.5
1.522
1.538
1.555
V
V
V
VIN = 2.3V, ILOAD = 1mA
2.8V < VIN < 20V, 1mA < ILOAD < 50mA
2.8V < VIN < 20V, 1mA < ILOAD < 100mA
●
●
1.775
1.750
1.725
1.8
1.8
1.8
1.825
1.845
1.860
V
V
V
VIN = 2.5V, ILOAD = 1mA
3V < VIN < 20V, 1mA < ILOAD < 50mA
3V < VIN < 20V, 1mA < ILOAD < 100mA
●
●
1.970
1.945
1.920
2
2
2
2.030
2.045
2.060
V
V
V
VIN = 3V, ILOAD = 1mA
3.5V < VIN < 20V, 1mA < ILOAD < 50mA
3.5V < VIN < 20V, 1mA < ILOAD < 100mA
●
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2.465
2.435
2.415
2.5
2.5
2.5
2.535
2.565
2.575
V
V
V
LT1761 Series
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2)
PARAMETER
CONDITIONS
Regulated Output Voltage
(Note 4)
LT1761-2.8
LT1761-3
LT1761-3.3
LT1761-5
MIN
TYP
MAX
UNITS
●
●
2.762
2.732
2.706
2.8
2.8
2.8
2.838
2.868
2.884
V
V
V
VIN = 3.5V, ILOAD = 1mA
4V < VIN < 20V, 1mA < ILOAD < 50mA
4V < VIN < 20V, 1mA < ILOAD < 100mA
●
●
2.960
2.930
2.900
3
3
3
3.040
3.070
3.090
V
V
V
VIN = 3.8V, ILOAD = 1mA
4.3V < VIN < 20V, 1mA < ILOAD < 50mA
4.3V < VIN < 20V, 1mA < ILOAD < 100mA
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3.250
3.230
3.190
3.3
3.3
3.3
3.350
3.370
3.400
V
V
V
VIN = 5.5V, ILOAD = 1mA
6V < VIN < 20V, 1mA < ILOAD < 50mA
6V < VIN < 20V, 1mA < ILOAD < 100mA
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4.935
4.900
4.850
5
5
5
5.065
5.100
5.120
V
V
V
VIN = 2V, ILOAD = 1mA
2.3V < VIN < 20V, 1mA < ILOAD < 50mA
2.3V < VIN < 20V, 1mA < ILOAD < 100mA
●
●
1.205
1.190
1.170
1.220
1.220
1.220
1.235
1.250
1.260
V
V
V
●
●
●
●
●
●
●
●
●
1
1
1
1
1
1
1
1
1
10
10
10
10
10
10
10
10
10
mV
mV
mV
mV
mV
mV
mV
mV
mV
10
20
35
30
55
mV
mV
mV
mV
20
35
30
60
mV
mV
mV
mV
20
35
35
65
mV
mV
mV
mV
20
35
40
80
mV
mV
mV
mV
20
38
40
86
mV
mV
mV
mV
20
40
40
90
mV
mV
mV
mV
VIN = 3.3V, ILOAD = 1mA
3.8V < VIN < 20V, 1mA < ILOAD < 50mA
3.8V < VIN < 20V, 1mA < ILOAD < 100mA
ADJ Pin Voltage
(Note 3, 4)
LT1761
Line Regulation
LT1761-1.5
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3
LT1761-5
LT1761(Note 3)
∆VIN = 2V to 20V, ILOAD = 1mA
∆VIN = 2.3V to 20V, ILOAD = 1mA
∆VIN = 2.5V to 20V, ILOAD = 1mA
∆VIN = 3V to 20V, ILOAD = 1mA
∆VIN = 3.3V 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
Load Regulation
LT1761-1.5
VIN = 2.5V, ∆ILOAD = 1mA to 50mA
VIN = 2.5V, ∆ILOAD = 1mA to 50mA
VIN = 2.5V, ∆ILOAD = 1mA to 100mA
VIN = 2.5V, ∆ILOAD = 1mA to 100mA
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
VIN = 2.8V, ∆ILOAD = 1mA to 50mA
VIN = 2.8V, ∆ILOAD = 1mA to 50mA
VIN = 2.8V, ∆ILOAD = 1mA to 100mA
VIN = 2.8V, ∆ILOAD = 1mA to 100mA
VIN = 3V, ∆ILOAD = 1mA to 50mA
VIN = 3V, ∆ILOAD = 1mA to 50mA
VIN = 3V, ∆ILOAD = 1mA to 100mA
VIN = 3V, ∆ILOAD = 1mA to 100mA
VIN = 3.5V, ∆ILOAD = 1mA to 50mA
VIN = 3.5V, ∆ILOAD = 1mA to 50mA
VIN = 3.5V, ∆ILOAD = 1mA to 100mA
VIN = 3.5V, ∆ILOAD = 1mA to 100mA
VIN = 3.8V, ∆ILOAD = 1mA to 50mA
VIN = 3.8V, ∆ILOAD = 1mA to 50mA
VIN = 3.8V, ∆ILOAD = 1mA to 100mA
VIN = 3.8V, ∆ILOAD = 1mA to 100mA
VIN = 4V, ∆ILOAD = 1mA to 50mA
VIN = 4V, ∆ILOAD = 1mA to 50mA
VIN = 4V, ∆ILOAD = 1mA to 100mA
VIN = 4V, ∆ILOAD = 1mA to 100mA
●
14
●
10
●
15
●
10
●
15
●
10
●
20
●
10
●
20
●
10
●
20
●
3
LT1761 Series
ELECTRICAL CHARACTERISTICS
The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. (Note 2)
PARAMETER
CONDITIONS
Load Regulation
LT1761-3.3
LT1761-5
MIN
VIN = 4.3V, ∆ILOAD = 1mA to 50mA
VIN = 4.3V, ∆ILOAD = 1mA to 50mA
VIN = 4.3V, ∆ILOAD = 1mA to 100mA
VIN = 4.3V, ∆ILOAD = 1mA to 100mA
VIN = 6V, ∆ILOAD = 1mA to 50mA
VIN = 6V, ∆ILOAD = 1mA to 50mA
VIN = 6V, ∆ILOAD = 1mA to 100mA
VIN = 6V, ∆ILOAD = 1mA to 100mA
LT1761 (Note 3) VIN = 2.3V, ∆ILOAD = 1mA to 50mA
VIN = 2.3V, ∆ILOAD = 1mA to 50mA
VIN = 2.3V, ∆ILOAD = 1mA to 100mA
VIN = 2.3V, ∆ILOAD = 1mA to 100mA
UNITS
10
20
40
40
100
mV
mV
mV
mV
30
60
65
150
mV
mV
mV
mV
6
12
12
50
mV
mV
mV
mV
20
●
15
●
25
●
1
●
1
●
ILOAD = 1mA
ILOAD = 1mA
●
(Notes 5, 6, 11)
ILOAD = 10mA
ILOAD = 10mA
●
ILOAD = 50mA
ILOAD = 50mA
●
ILOAD = 100mA
ILOAD = 100mA
●
GND Pin Current
VIN = VOUT(NOMINAL)
(Notes 5, 7)
ILOAD = 0mA
ILOAD = 1mA
ILOAD = 10mA
ILOAD = 50mA
ILOAD = 100mA
●
●
●
●
●
Output Voltage Noise
COUT = 10µF, CBYP = 0.01µF, ILOAD = 100mA, BW = 10Hz to 100kHz
0.10
0.15
0.19
V
V
0.17
0.22
0.29
V
V
0.24
0.28
0.38
V
V
0.30
0.35
0.45
V
V
20
55
230
1
2.2
45
100
400
2
4
µA
µA
µA
mA
mA
µVRMS
20
ADJ Pin Bias Current
(Notes 3, 8)
Shutdown Threshold
VOUT = Off to On
VOUT = On to Off
●
●
SHDN Pin Current
(Note 9)
VSHDN = 0V
VSHDN = 20V
●
●
Quiescent Current in Shutdown
VIN = 6V, VSHDN = 0V
Ripple Rejection (Note 3)
VIN – VOUT = 1.5V (Avg), VRIPPLE = 0.5VP-P, fRIPPLE = 120Hz,
ILOAD = 50mA
Current Limit
VIN = 7V, VOUT = 0V
VIN = VOUT(NOMINAL) + 1V, ∆VOUT = – 5%
●
Input Reverse Leakage Current
VIN = – 20V, VOUT = 0V
●
Reverse Output Current
(Note 10)
LT1761-1.5
VOUT = 1.5V, VIN < 1.5V
LT1761-1.8
VOUT = 1.8V, VIN < 1.8V
LT1761-2
VOUT = 2V, VIN < 2V
LT1761-2.5
VOUT = 2.5V, VIN < 2.5V
LT1761-2.8
VOUT = 2.8V, VIN < 2.8V
LT1761-3
VOUT = 3V, VIN < 3V
LT1761-3.3
VOUT = 3.3V, VIN < 3.3V
LT1761-5
VOUT = 5V, VIN < 5V
LT1761 (Note 3) VOUT = 1.22V, VIN < 1.22V
4
MAX
●
Dropout Voltage
VIN = VOUT(NOMINAL)
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LT1761 regulators are tested and specified under pulse load
conditions such that TJ ≈ TA. The LT1761 is 100% production tested at
TYP
0.25
55
30
100
nA
0.8
0.65
2
V
V
0
1
0.5
3
µA
µA
0.01
0.1
µA
65
dB
200
mA
mA
110
10
10
10
10
10
10
10
10
5
1
mA
20
20
20
20
20
20
20
20
10
µA
µA
µA
µA
µA
µA
µA
µA
µA
TA = 25°C. Performance at – 40°C and 125°C is assured by design,
characterization and correlation with statistical process controls.
Note 3: The LT1761 (adjustable versions) are tested and specified for
these conditions with the ADJ pin connected to the OUT pin.
LT1761 Series
ELECTRICAL CHARACTERISTICS
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 LT1761
(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 5µA DC load on the output.
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 or at the minimum input
voltage specification. 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 LT1761, LT1761-1.5, LT1761-1.8 and LT1761-2 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.
U W
TYPICAL PERFOR A CE CHARACTERISTICS
500
450
450
400
400
TJ = 125°C
300
250
TJ = 25°C
200
150
500
= TEST POINTS
450
DROPOUT VOLTAGE (mV)
500
350
TJ ≤ 125°C
350
300
TJ ≤ 25°C
250
200
150
400
350
250
150
100
50
50
50
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
1761 G00
20
15
10
1.83
1.514
1.82
1.507
1.500
1.493
1.486
1.479
5
0
–50 –25
IL = 1mA
1.521
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
VSHDN = VIN
VSHDN = 0V
0
25
50
75
100
125
1.472
–50 –25
1761 G03
1.81
1.80
1.79
1.78
1.77
0
25
50
75
100
125
TEMPERATURE (°C)
TEMPERATURE (°C)
125
1.84
IL = 1mA
VIN = 6V
RL = ∞ (250k FOR LT1761-BYP, -SD)
IL = 0 (5µA FOR LT1761-BYP, -SD)
100
LT1761-1.8
Output Voltage
1.528
40
25
50
25
0
75
TEMPERATURE (°C)
1761 G01.1
LT1761-1.5
Output Voltage
30
IL = 1mA
1761 G01
Quiescent Current
35
IL = 10mA
0
–50 –25
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
IL = 50mA
200
100
0
IL = 100mA
300
100
0
QUIESCENT CURRENT (µA)
Dropout Voltage
Guaranteed Dropout Voltage
DROPOUT VOLTAGE (mV)
DROPOUT VOLTAGE (mV)
Typical Dropout Voltage
1.76
–50 –25
0
25
50
75
100
125
TEMPERATURE (°C)
1761 G51
1761 G06
5
LT1761 Series
U W
TYPICAL PERFOR A CE CHARACTERISTICS
LT1761-2.5
Output Voltage
LT1761-2
Output Voltage
2.04
2.54
2.84
IL = 1mA
IL = 1mA
IL = 1mA
2.53
2.83
2.02
2.52
2.82
2.01
2.00
1.99
1.98
1.97
OUTPUT VOLTAGE (V)
2.03
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
LT1761-2.8
Output Voltage
2.51
2.50
1.49
1.48
1.47
1.96
–50 –25
0
25
50
75
100
0
TEMPERATURE (°C)
25
50
75
100
2.78
2.76
–50 –25
125
3.330
5.04
OUTPUT VOLTAGE (V)
3.030
OUTPUT VOLTAGE (V)
5.06
2.955
3.315
3.300
3.285
3.270
25
50
75
100
125
3.240
–50 –25
0
TEMPERATURE (°C)
25
50
75
1.220
1.215
1.210
75
100
125
1761 G10
6
125
100
75
50
VSHDN = VIN
125
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
150
125
100
75
50
VSHDN = VIN
25
VSHDN = 0V
0
TEMPERATURE (°C)
100
TJ = 25°C
RL = ∞
175
150
25
1.205
75
200
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
1.225
50
LT1761-1.8
Quiescent Current
TJ = 25°C
RL = ∞
175
1.230
25
1761 G12
200
50
0
TEMPERATURE (°C)
LT1761-1.5
Quiescent Current
IL = 1mA
25
4.96
1761 G11
1.240
0
4.98
TEMPERATURE (°C)
LT1761-BYP, LT1761-SD
ADJ Pin Voltage
1.200
–50 –25
5.00
4.92
–50 –25
125
100
1761 G09
1.235
5.02
4.94
3.255
0
125
IL = 1mA
3.345
2.970
100
5.08
3.045
2.985
75
LT1761-5
Output Voltage
IL = 1mA
3.000
50
1761 G52
3.360
IL = 1mA
3.015
25
TEMPERATURE (°C)
LT1761-3.3
Output Voltage
3.060
2.940
–50 –25
0
1761 G08
LT1761-3
Output Voltage
OUTPUT VOLTAGE (V)
2.79
TEMPERATURE (°C)
1761 G07
ADJ PIN VOLTAGE (V)
2.80
2.77
1.46
–50 –25
125
2.81
VSHDN = 0V
0
9
10
1761 G53
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1761 G18
LT1761 Series
U W
TYPICAL PERFOR A CE CHARACTERISTICS
LT1761-2
Quiescent Current
200
200
TJ = 25°C
RL = ∞
125
100
75
50
VSHDN = VIN
25
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
150
125
100
75
50
VSHDN = VIN
25
VSHDN = 0V
0
10
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
9
8
100
75
50
VSHDN = VIN
3 4 5 6 7
INPUT VOLTAGE (V)
8
150
125
100
75
50
VSHDN = VIN
0
10
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
9
8
4
50
1761 G17
VSHDN = 0V
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1761 G16
1.75
RL = 15Ω
IL = 100mA*
1.50
1.25
RL = 30Ω
IL = 50mA*
1.00
0.75
RL = 1.5k
IL = 1mA*
TJ = 25°C
*FOR VOUT = 1.8V
2.25
2.00
1.75
RL = 18Ω
IL = 100mA*
1.50
1.25
RL = 36Ω
IL = 50mA*
1.00
0.75
RL = 1.8k
IL = 1mA*
0.50
RL = 150Ω
IL = 10mA*
0.25
0
6 8 10 12 14 16 18 20
INPUT VOLTAGE (V)
VSHDN = VIN
LT1761-1.8
GND Pin Current
2.00
0.25
VSHDN = 0V
2
75
2.50
0.50
5
0
100
0
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
QUIESCENT CURRENT (µA)
10
0
125
10
TJ = 25°C
*FOR VOUT = 1.5V
2.25
15
10
TJ = 25°C
RL = ∞
0
2.50
TJ = 25°C
RL = 250k
IL = 5µA
9
150
LT1761-1.5
GND Pin Current
30
20
8
1761 G15
LT1761-BYP, LT1761-SD
Quiescent Current
VSHDN = VIN
3 4 5 6 7
INPUT VOLTAGE (V)
25
VSHDN = 0V
1761 G14
25
2
LT1761-5
Quiescent Current
175
0
9
1
200
25
VSHDN = 0V
2
VSHDN = 0V
1761 G54
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
QUIESCENT CURRENT (µA)
125
VSHDN = VIN
0
TJ = 25°C
RL = ∞
175
150
1
50
10
200
TJ = 25°C
RL = ∞
0
75
LT1761-3.3
Quiescent Current
200
0
100
1761 G13
LT1761-3
Quiescent Current
25
125
0
1761 G19
175
150
25
VSHDN = 0V
0
9
TJ = 25°C
RL = ∞
175
QUIESCENT CURRENT (µA)
150
0
200
TJ = 25°C
RL = ∞
175
QUIESCENT CURRENT (µA)
175
QUIESCENT CURRENT (µA)
LT1761-2.8
Quiescent Current
LT1761-2.5
Quiescent Current
RL = 180Ω
IL = 10mA*
0
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1761 G55
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1761 G02
7
LT1761 Series
U W
TYPICAL PERFOR A CE CHARACTERISTICS
LT1761-2
GND Pin Current
2.50
TJ = 25°C
*FOR VOUT = 2V
2.25
GND PIN CURRENT (mA)
2.00
RL = 20Ω
IL = 100mA*
1.75
1.50
1.25
RL = 40Ω
IL = 50mA*
1.00
0.75
RL = 2k
IL = 1mA*
0.50
0.25
1.75
1.50
1.25
RL = 50Ω
IL = 50mA*
1.00
0.75
RL = 2.5k
IL = 1mA*
0.25
RL = 250Ω
IL = 10mA*
0
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
0
10
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
RL = 60Ω
IL = 50mA*
0.75
RL = 3k
IL = 1mA*
0.50
0.25
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
1.75
RL = 33Ω
IL = 100mA*
1.50
1.25
RL = 66Ω
IL = 50mA*
1.00
0.75
10
RL = 3.3k
IL = 1mA*
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
RL = 24.4Ω
IL = 50mA*
1.00
0.75
RL = 1.22k
IL = 1mA*
0.50
0.25
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
0.75
10
1761 G24
RL = 5k
IL = 1mA*
0
RL = 500Ω
IL = 10mA*
1
2
3 4 5 6 7
INPUT VOLTAGE (V)
8
9
10
1761 G23
0.9
2.00
1.75
1.50
1.25
1.00
0.75
0.25
9
RL = 100Ω
IL = 50mA*
1.00
1.0
IL = 1mA
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1
1.25
SHDN Pin Threshold
(On-to-Off)
0.50
RL = 122Ω
IL = 10mA*
0
0
1.50
10
SHDN PIN THRESHOLD (V)
GND PIN CURRENT (mA)
1.25
10
RL = 50Ω
IL = 100mA
1.75
0.25
VIN = VOUT(NOMINAL) + 1V
2.25
1.50
9
TJ = 25°C
*FOR VOUT = 5V
0.50
RL = 330Ω
IL = 10mA*
2.50
TJ = 25°C
*FOR VOUT = 1.22V
1.75
8
2.00
GND Pin Current vs ILOAD
RL = 12.2Ω
IL = 100mA*
3 4 5 6 7
INPUT VOLTAGE (V)
1761 G22
2.50
2.00
2
0
0
LT1761-BYP, LT1761-SD
GND Pin Current
2.25
1
1761 G56
2.25
2.00
0.25
9
RL = 280Ω
IL = 10mA*
LT1761-5
GND Pin Current
1761 G21
GND PIN CURRENT (mA)
0
0
1
RL = 2.8k
IL = 1mA*
2.50
0.50
RL = 300Ω
IL = 10mA*
0
0
0.75
10
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
GND PIN CURRENT (mA)
RL = 30Ω
IL = 100mA*
1.25
8
9
TJ = 25°C
*FOR VOUT = 3.3V
2.25
2.00
RL = 56Ω
IL = 50mA*
1.00
0.25
2.50
TJ = 25°C
*FOR VOUT = 3V
1.00
1.25
LT1761-3.3
GND Pin Current
2.50
1.50
1.50
1761 G20
LT1761-3
GND Pin Current
2.25
RL = 28Ω
IL = 100mA
1.75
0
8
1761 G04
1.75
2.00
0.50
0
0
TJ = 25°C
*FOR VOUT = 2.8V
2.25
RL = 25Ω
IL = 100mA
2.00
0.50
RL = 200Ω
IL = 10mA*
2.50
TJ = 25°C
*FOR VOUT = 2.5V
2.25
GND PIN CURRENT (mA)
2.50
GND PIN CURRENT (mA)
LT1761-2.8
GND Pin Current
LT1761-2.5
GND Pin Current
0
10 20 30 40 50 60 70 80 90 100
OUTPUT CURRENT (mA)
1761 G25
0
–50 –25
50
0
75
25
TEMPERATURE (°C)
100
125
1761 G26
LT1761 Series
U W
TYPICAL PERFOR A CE CHARACTERISTICS
0.9
0.9
IL = 100mA
0.7
0.6
IL = 1mA
0.5
0.4
0.3
0.2
0.1
1.4
VSHDN = 20V
SHDN PIN INPUT CURRENT (µA)
1.0
0.8
SHDN Pin Input Current
SHDN Pin Input Current
1.0
SHDN PIN INPUT CURRENT (µA)
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
0
1
2
3 4 5 6 7 8
SHDN PIN VOLTAGE (V)
9
1761 G27
80
70
60
50
40
30
20
10
VOUT = 0V
TJ = 25°C
300
100
200
150
100
50
125
0
2
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
1
4
3
2
5
INPUT VOLTAGE (V)
200
150
100
0
–50 –25
7
6
REVERSE OUTPUT CURRENT (µA)
1761 G33
50
25
0
75
TEMPERATURE (°C)
100
7.5
1761 G32
Input Ripple Rejection
LT1761-BYP,-SD
70
LT1761-BYP
60
LT1761-5
LT1761-1.5,-1.8,-2,
-2.5,-2.8,-3,-3.3,-5
IL = 100mA
VIN = VOUT(NOMINAL) +
1V + 50mVRMS RIPPLE
CBYP = 0
50
COUT = 10µF
40
30
20
5.0
0
–50 –25
125
80
VIN = 0V
22.5 VOUT = 1.22V (LT1761-BYP, -SD)
VOUT = 1.5V (LT1761-1.5)
20.0 VOUT = 1.8V (LT1761-1.8)
V
= 2V (LT1761-2)
17.5 VOUT = 2.5V (LT1761-2.5)
OUT
V
15.0 OUT = 2.8V (LT1761-2.8)
VOUT = 3V (LT1761-3)
12.5 VOUT = 3.3V (LT1761-3.3)
VOUT = 5V (LT1761-5)
10.0
2.5
10
VIN = 7V
VOUT = 0V
1761 G31
LT1761-BYP
LT1761-SD
125
50
25.0
LT1761-5
1
100
250
Reverse Output Current
LT1761-3.3
50
25
0
75
TEMPERATURE (°C)
300
250
Reverse Output Current
0
0.2
Current Limit
1761 G30
0
0.4
350
0
50
0
75
25
TEMPERATURE (°C)
10
0.6
1761 G29
CURRENT LIMIT (mA)
SHORT-CIRCUIT CURRENT (mA)
ADJ PIN BIAS CURRENT (nA)
90
REVERSE OUTPUT CURRENT (µA)
10
350
TJ = 25°C
90 VIN = 0V
CURRENT FLOWS
80 INTO OUTPUT PIN
70 VOUT = VADJ
(LT1761-BYP, -SD)
60
LT1761-1.5
LT1761-1.8
50
LT1761-2
40
LT1761-2.5
LT1761-2.8
30
LT1761-3
20
0.8
Current Limit
ADJ Pin Bias Current
100
1.0
1761 G28
100
0
–50 –25
1.2
0
–50 –25
0
125
RIPPLE REJECTION (dB)
SHDN PIN THRESHOLD (V)
SHDN Pin Threshold
(Off-to-On)
COUT = 1µF
10
0
50
0
75
25
TEMPERATURE (°C)
100
125
1761 G34
10
100
1k
10k
FREQUENCY (Hz)
100k
1M
1761 G35
9
LT1761 Series
U W
TYPICAL PERFOR A CE CHARACTERISTICS
LT1761-5
Input Ripple Rejection
80
2.5
80
CBYP = 0.01µF
70
CBYP = 1000pF
RIPPLE REJECTION (dB)
60
50
CBYP = 100pF
40
30
20
IL = 100mA
VIN = VOUT(NOMINAL) +
1V + 50mVRMS RIPPLE
COUT = 10µF
10
60
50
40
30
100
VIN = VOUT (NOMINAL) +
1V + 0.5VP-P RIPPLE
AT f = 120Hz
IL = 50mA
20
10
0
10
100k
1k
10k
FREQUENCY (Hz)
MINIMUM INPUT VOLTAGE (V)
70
RIPPLE REJECTION (dB)
LT1761-BYP, LT1761-SD
Minimum Input Voltage
Input Ripple Rejection
0
–50 –25
1M
25
0
50
75
100
IL = 100mA
1.5
IL = 50mA
1.0
0.5
0
–50 –25
125
50
0
75
25
TEMPERATURE (°C)
TEMPERATURE (°C)
1761 G36
100
125
1761 G38
1761 G37
Load Regulation
∆IL = 1mA to 50mA
Load Regulation
∆IL = 1mA to 100mA
0
LT1761-BYP, -SD
LT1761-1.5
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3
–5
–10
–15
–20
–25
– 30
LT1761-5
LOAD REGULATION (mV)
0
LOAD REGULATION (mV)
2.0
–10
LT1761-BYP, -SD
–20
LT1761-1.5
LT1761-1.8
LT1761-2
LT1761-2.5
LT1761-2.8
LT1761-3
LT1761-3.3
–30
–40
–50
–60
–70
LT1761-5
–80
–35
–40
–50 –25
–90
0
25
50
75
100
–100
–50 –25
125
TEMPERATURE (°C)
0
25
50
75
1761 G39
1
LT1761-BYP, -SD
LT1761-1.5
LT1761-1.8
LT1761-2
COUT = 10µF
CBYP = 0
IL = 100mA
0.01
10
100
1k
10k
FREQUENCY (Hz)
100k
1761 G41
10
RMS Output Noise vs
Bypass Capacitor
140
10
COUT = 10µF
IL = 100mA
f = 10Hz TO 100kHz
LT1761-5
120
LT1761-5
CBYP = 1000pF
1
CBYP = 100pF
LT1761-BYP
0.1
CBYP = 0.01µF
LT1761-3.3
LT1761-3
100
LT1761-2.8
LT1761-2.5
80
60
40
LT1761-1.8, -2
20
COUT = 10µF
IL = 100mA
0.01
10
OUTPUT NOISE (µVRMS)
OUTPUT NOISE SPECTRAL DENSITY (µV/√Hz)
OUTPUT NOISE SPECTRAL DENSITY (µV/√Hz)
LT1761-3.3
LT1761-2.8,-3
LT1761-2.5
LT1761-5
0.1
1761 G40
Output Noise Spectral Density
Output Noise Spectral Density
10
125
100
TEMPERATURE (°C)
LT1761-1.5
LT1761-BYP
0
100
1k
10k
FREQUENCY (Hz)
100k
10
100
1k
10k
CBYP (pF)
1761 G42
1761 G43
LT1761 Series
U W
TYPICAL PERFOR A CE CHARACTERISTICS
LT1761-5
10Hz to 100kHz Output Noise
CBYP = 100pF
LT1761-5
10Hz to 100kHz Output Noise
CBYP = 0
RMS Output Noise vs
Load Current (10Hz to 11kHz)
160
COUT = 10µF
CBYP = 0
CBYP = 0.01µF
LT1761-5
120
VOUT
100µV/DIV
VOUT
100µV/DIV
100
80
LT1761-BYP
60
40
LT1761-5
20
1ms/DIV
1ms/DIV
COUT = 10µF
IL = 100mA
LT1761-BYP
10
0.1
1
LOAD CURRENT (mA)
COUT = 10µF
IL = 100mA
1761 G45
1761 G46
100
1761 G44
LT1761-5
10Hz to 100kHz Output Noise
CBYP = 1000pF
LT1761-5
10Hz to 100kHz Output Noise
CBYP = 0.01µF
VOUT
100µV/DIV
VOUT
100µV/DIV
1ms/DIV
1ms/DIV
COUT = 10µF
IL = 100mA
COUT = 10µF
IL = 100mA
1761 G47
VIN = 6V
CIN = 10µF
COUT = 10µF
0.2
0.1
0
–0.1
LOAD CURRENT
(mA)
–0.2
100
50
0
0
400
800
1200
TIME (µs)
1600
1761 G48
LT1761-5 Transient Response
CBYP = 0.01µF
OUTPUT VOLTAGE
DEVIATION (V)
LT1761-5 Transient Response
CBYP = 0
OUTPUT VOLTAGE
DEVIATION (V)
0
0.01
LOAD CURRENT
(mA)
OUTPUT NOISE (µVRMS)
140
2000
1761 G49
VIN = 6V
CIN = 10µF
COUT = 10µF
0.04
0.02
0
–0.02
–0.04
100
50
0
0
20 40 60 80 100 120 140 160 180 200
TIME (µs)
1761 G50
11
LT1761 Series
U
U
U
PI FU CTIO S
IN (Pin 1): 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 1µF to 10µF is sufficient. The
LT1761 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.
GND (Pin 2): Ground.
SHDN (Pin 3, Fixed/-SD Devices): Shutdown. The SHDN
pin is used to put the LT1761 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 open-collector logic with a pull-up resistor. The
pull-up resistor is required to supply the pull-up current of
the open-collector gate, normally several microamperes,
and the SHDN pin current, typically 1µA. If unused, the
SHDN pin must be connected to VIN. The device will not
function if the SHDN pin is not connected. For the
LT1761-BYP, the SHDN pin is internally connected to VIN.
BYP (Pins 3/4, Fixed/-BYP Devices): Bypass. The BYP
pin is used to bypass the reference of the LT1761 regulators to achieve low noise performance from the regulator.
The BYP pin is clamped internally to ±0.6V (one VBE) from
ground. A small capacitor from the output to this pin will
bypass the reference to lower the output voltage noise. A
maximum value of 0.01µF can be used for reducing output
voltage noise to a typical 20µVRMS over a 10Hz to 100kHz
bandwidth. If not used, this pin must be left unconnected.
ADJ (Pin 4, Adjustable Devices Only): Adjust Pin. For the
adjustable LT1761, 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.
OUT (Pin 5): Output. The output supplies power to the
load. A minimum output capacitor of 1µF 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.
U
W
U U
APPLICATIO S I FOR ATIO
The LT1761 series are 100mA low dropout regulators with
micropower quiescent current and shutdown. The devices
are capable of supplying 100mA at a dropout voltage of
300mV. Output voltage noise can be lowered to 20µVRMS
over a 10Hz to 100kHz bandwidth with the addition of a
0.01µF 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 (20µA)
drops to less than 1µA in shutdown. In addition to the low
quiescent current, the LT1761 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
12
up by a backup battery when the input is pulled to ground,
the LT1761-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 LT1761 has an output
voltage range of 1.22V to 20V. The output voltage is set by
the ratio of two external resistors as shown in Figure 1. The
device servos the output to maintain the ADJ pin voltage
at 1.22V referenced to ground. The current in R1 is then
LT1761 Series
U
W
U U
APPLICATIO S I FOR ATIO
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
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 100mA is –1mV typical
at VOUT = 1.22V. At VOUT = 12V, load regulation is:
(12V/1.22V)(–1mV) = – 9.8mV
IN
VIN
OUT
VOUT
+
R2
LT1761
 R2 
VOUT = 1.22V  1 +  + IADJ R2
 R1
( )( )
VADJ = 1.22V
ADJ
GND
R1
IADJ = 30nA AT 25°C
OUTPUT RANGE = 1.22V TO 20V
1761 F01
Figure 1. Adjustable Operation
Bypass Capacitance and Low Noise Performance
The LT1761 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 20µVRMS with the addition
of a 0.01µF bypass capacitor. Using a bypass capacitor
has the added benefit of improving transient response.
With no bypass capacitor and a 10µF output capacitor, a
10mA to 100mA load step will settle to within 1% of its final
value in less than 100µs. With the addition of a 0.01µF
bypass capacitor, the output will stay within 1% for a 10mA
to 100mA load step (see LT1761-5 Transient Reponse in
Typical Performance Characteristics section). However,
regulator start-up time is inversely proportional to the size
of the bypass capacitor, slowing to 15ms with a 0.01µF
bypass capacitor and 10µF output capacitor.
Output Capacitance and Transient Response
The LT1761 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 1µF with an
ESR of 3Ω or less is recommended to prevent oscillations. The LT1761-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
LT1761-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,
2.2µF of output capacitor is recommended. With a 330pF
bypass capacitor or larger, a 3.3µF output capacitor is
recommended. The shaded region of Figure 2 defines the
region over which the LT1761 regulators are stable. The
minimum ESR needed is defined by the amount of
bypass capacitance used, while the maximum ESR is 3Ω.
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
4.0
3.5
3.0
STABLE REGION
2.5
ESR (Ω)
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 25°C, flows through R2 into the ADJ pin. The
output voltage can be calculated using the formula in
Figure 1. 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.
2.0
CBYP = 0
CBYP = 100pF
CBYP = 330pF
CBYP > 3300pF
1.5
1.0
0.5
0
1
3
2
4 5 6 7 8 9 10
OUTPUT CAPACITANCE (µF)
1761 F02
Figure 2. Stability
13
LT1761 Series
U
W
U U
APPLICATIO S I FOR ATIO
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 3 and 4. When
used with a 5V regulator, a 10µF Y5V capacitor can exhibit
an effective value as low as 1µF to 2µF 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 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 5’s trace in response to light tapping
from a pencil. Similar vibration induced behavior can
masquerade as increased output voltage noise.
LT1761-5
COUT = 10µF
CBYP = 0.01µF
ILOAD = 100mA
VOUT
500µV/DIV
100ms/DIV
20
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
1761 F05
Figure 5. Noise Resulting from Tapping on a Ceramic Capacitor
0
CHANGE IN VALUE (%)
X5R
Thermal Considerations
–20
The power handling capability of the device will be limited
by the maximum rated junction temperature (125°C). The
power dissipated by the device will be made up of two
components:
–40
–60
Y5V
–80
–100
0
2
4
14
8
6
10 12
DC BIAS VOLTAGE (V)
16
1761 F03
Figure 3. Ceramic Capacitor DC Bias Characteristics
40
CHANGE IN VALUE (%)
20
X5R
0
–20
–40
Y5V
–60
–80
BOTH CAPACITORS ARE 16V,
1210 CASE SIZE, 10µF
–100
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1761 F04
Figure 4. Ceramic Capacitor Temperature Characteristics
14
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 ground pin current can be found by examining the
GND Pin Current curves in the Typical Performance Characteristics section. Power dissipation will be equal to the
sum of the two components listed above.
The LT1761 series regulators have internal thermal limiting designed to protect the device during overload conditions. For continuous normal conditions, the maximum
junction temperature rating of 125°C 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
LT1761 Series
U
U
W
U
APPLICATIONS INFORMATION
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.
Table 1. Measured Thermal Resistance
COPPER AREA
TOPSIDE*
BACKSIDE
BOARD AREA
THERMAL RESISTANCE
(JUNCTION-TO-AMBIENT)
2500mm
2500mm
2
2500mm2
125°C/W
1000mm2
2500mm2
2500mm2
125°C/W
2
2
2
225mm
2
2500mm
130°C/W
100mm2
2500mm
2500mm2
2500mm2
135°C/W
50mm2
2500mm2
2500mm2
150°C/W
*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 50mA
and a maximum ambient temperature of 50°C, 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) = 50mA
VIN(MAX) = 6V
IGND at (IOUT = 50mA, VIN = 6V) = 1mA
So,
P = 50mA(6V – 3.3V) + 1mA(6V) = 0.14W
The thermal resistance will be in the range of 125°C/W to
150°C/W depending on the copper area. So the junction
temperature rise above ambient will be approximately
equal to:
0.14W(150°C/W) = 21.2°C
The maximum junction temperature will then be equal to
the maximum junction temperature rise above ambient
plus the maximum ambient temperature or:
TJMAX = 50°C + 21.2°C = 71.2°C
Protection Features
The LT1761 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
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 125°C.
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 100µA) 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 LT1761-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 500kΩ or higher, limiting current
flow to typically less than 100µA. 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.
15
LT1761 Series
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.
100
REVERSE OUTPUT CURRENT (µA)
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.
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 6.
LT1761-BYP
LT1761-SD
LT1761-3.3
10
When the IN pin of the LT1761-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 2µA. 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
U
PACKAGE DESCRIPTIO
TJ = 25°C
90 VIN = 0V
CURRENT FLOWS
80 INTO OUTPUT PIN
70 VOUT = VADJ
(LT1761-BYP, -SD)
60
LT1761-1.5
LT1761-1.8
50
LT1761-2
40
LT1761-2.5
LT1761-2.8
30
LT1761-3
20
LT1761-5
0
0
1
2
3 4 5 6 7 8
OUTPUT VOLTAGE (V)
9
10
1761 F06
Figure 6. Reverse Output Current
Dimensions in inched (millimeters) unless otherwise noted.
2.60 – 3.00
(0.102 – 0.118)
1.50 – 1.75
(0.059 – 0.069)
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
0.35 – 0.55
(0.014 – 0.022)
0.00 – 0.15
(0.00 – 0.006)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
0.90 – 1.45
(0.035 – 0.057)
0.35 – 0.50
0.90 – 1.30
(0.014 – 0.020)
(0.035 – 0.051)
FIVE PLACES (NOTE 2)
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
1.90
(0.074)
REF
0.95
(0.037)
REF
S5 SOT-23 0599
RELATED PARTS
PART NUMBER
LT1120
LT1121
LT1129
LT1175
LT1521
LT1529
LT1762 Series
LT1763 Series
LTC1928
LT1962 Series
LT1963
LT1764
LTC3404
DESCRIPTION
125mA Low Dropout Regulator with 20µA 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 50µA IQ
150mA, Low Noise, LDO Micropower Regulator
500mA, Low Noise, LDO Micropower Regulator
Doubler Charge Pump with Low Noise Linear Regulator
300mA, Low Noise, LDO Micropower Regulator
1.5A, Low Noise, Fast Transient Response LDO
3A, Low Noise, Fast Transient Response LDO
High Efficiency Synchronous Step-Down Switching Regulator
COMMENTS
Includes 2.5V Reference and Comparator
30µA IQ, SOT-223 Package
50µA Quiescent Current
45µA IQ, 0.26V Dropout Voltage, SOT-223 Package
15µA IQ, Reverse Battery Protection
500mV Dropout Voltage
25µA Quiescent Current, 20µVRMS Noise
30µA Quiescent Current, 20µVRMS Noise
Low Output Noise: 60µVRMS (100kHz BW)
30µA Quiescent Current, 20µVRMS Noise
40µVRMS, SOT-223 Package
40µVRMS, 340mV Dropout Voltage
Burst ModeTM Operation, Monolithic, 100% Duty Cycle
Burst Mode is a trademark of Linear Technology Corporation.
16
Linear Technology Corporation
1761fa LT/TP 0401 2K REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 1999
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