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LTC1538CG-AUX

Part # LTC1538CG-AUX
Description IC REG CTRLR BUCK PWM CM 28-SSOP
Category IC
Availability In Stock
Qty 85
Qty Price
1 - 17 $9.35307
18 - 35 $7.43994
36 - 53 $7.01480
54 - 71 $6.51881
72 + $5.81024
Manufacturer Available Qty
Linear Technology
Date Code: 9825
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Technical Document


DISCLAIMER: The information provided herein is solely for informational purposes. Customers must be aware of the suitability of this product for their application, and consider that variable factors such as Manufacturer, Product Category, Date Codes, Pictures and Descriptions may differ from available inventory.

4
LTC1538-AUX/LTC1539
ELECTRICAL CHARACTERISTICS
T
A
= 25°C, V
IN
= 15V, V
RUN/SS1,2
= 5V unless otherwise noted.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Low-Battery Comparator
V
SATLBO
LBO Saturation Voltage I
LBO
= 1.6mA, V
LBI
= 1.1V 0.6 1 V
I
LLBO
LBO Leakage V
LBO
= 12V, V
LBI
= 1.4V 0.01 1 µA
V
THLB1
LBI Trip Voltage High to Low Transition on LBO 1.16 1.19 1.22 V
I
INLB1
LBI Input Current V
LBI
= 1.19V 150 nA
V
HYSLBO
LBO Hysteresis 20 mV
Auxiliary Regulator/Comparator
I
AUXDR
AUXDR Current V
EXTVCC
= 0V
Max Current Sinking Capability V
AUXDR
= 4V, V
AUXFB
= 1.0V, V
AUXON
= 5V 10 15 mA
Control Current V
AUXDR
= 5V, V
AUXFB
= 1.5V, V
AUXON
= 5V 1 5 µA
Leakage when OFF V
AUXDR
= 24V, V
AUXFB
= 1.5V, V
AUXON
= 0V 0.01 1 µA
I
INAUXFB
AUXFB Input Current V
AUXFB
= 1.19V, V
AUXON
= 5V 0.01 1 µA
I
INAUXON
AUXON Input Current V
AUXON
= 5V 0.01 1 µA
V
THAUXON
AUXON Trip Voltage V
AUXDR
= 4V, V
AUXFB
= 1V 1.0 1.19 1.4 V
V
SATAUXDR
AUXDR Saturation Voltage I
AUXDR
= 1.6mA, V
AUXFB
= 1V, V
AUXON
= 5V 0.4 0.8 V
V
AUXFB
AUXFB Voltage V
AUXON
= 5V, 11V < V
AUXDR
< 24V (Note 5) 11.5 12.00 12.5 V
V
AUXON
= 5V, 3V < V
AUXDR
< 7V 1.14 1.19 1.24 V
V
THAUXDR
AUXFB Divider Disconnect Voltage V
AUXON
= 5V (Note 5); Ramping Negative 7.5 8.5 9.5 V
The denotes specifications which apply over the full operating
temperature range.
Note 1: T
J
is calculated from the ambient temperature T
A
and power
dissipation P
D
according to the following formulas:
LTC1538CG-AUX: T
J
= T
A
+ (P
D
)(95°C/W)
LTC1539CGW: T
J
= T
A
+ (P
D
)(85°C/W)
Note 2: The LTC1538-AUX and LTC1539 are tested in a feedback loop
which servos V
OSENSE1,2
to the balance point for the error amplifier
(V
ITH1,2
= 1.19V).
Note 3: Dynamic supply current is higher due to the gate charge being
delivered at the switching frequency. See Applications Information.
Note 4: Oscillator frequency is tested by measuring the C
OSC
charge and
discharge current (I
OSC
) and applying the formula:
f
OSC
(kHz) = 8.4(10
8
)[C
OSC
(pF) + 11]
-1
(1/I
CHG
+ 1/I
DISC
)
–1
Note 5: The auxiliary regulator is tested in a feedback loop which servos
V
AUXFB
to the balance point for the error amplifier. For applications with
V
AUXDR
> 9.5V, V
AUXFB
uses an internal resistive divider. See Applications
Information section.
5
LTC1538-AUX/LTC1539
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
Adaptive Power and Burst Mode are trademarks of Linear Technology Corporation.
INPUT VOLTAGE (V)
0
70
EFFICIENCY (%)
75
80
85
90
100
5
10 15 20
1538/39 • G01
25 30
95
I
LOAD
= 1A
I
LOAD
= 100mA
V
OUT
= 3.3V
LOAD CURRENT (A)
0.001
50
EFFICIENCY (%)
55
65
70
75
100
85
0.01 0.1
1
1538/39 • G03
60
90
95
80
10
Adaptive Power
TM
MODE
CONTINUOUS
MODE
V
IN
= 10V
V
OUT
= 5V
R
SENSE
= 0.33
Burst Mode
TM
OPERATION
Efficiency vs Load Current
Efficiency vs Input Voltage:
V
OUT
= 3.3V
INPUT VOLTAGE (V)
0
70
EFFICIENCY (%)
75
80
85
90
100
5
10 15 20
1538/39 • G02
25 30
95
I
LOAD
= 1A
I
LOAD
= 100mA
V
OUT
= 5V
Efficiency vs Input Voltage:
V
OUT
= 5V
V
ITH
Pin Voltage vs Output Current
V
IN
– V
OUT
Dropout Voltage vs
Load Current Load Regulation
LOAD CURRENT (A)
0
0
V
IN
– V
OUT
(V)
0.2
0.1
0.3
0.4
0.5
0.5 1.0 1.5 2.0
1538/39 • G04
2.5 3.0
R
SENSE
= 0.033
V
OUT
DROP OF 5%
LOAD CURRENT (A)
0
V
OUT
(%)
0
0.5
1.0 1.5 2.0
1538/39 • G05
2.5 3.0
0.25
0.50
0.75
–1.00
–1.25
–1.50
R
SENSE
= 0.033
OUTPUT CURRENT (%)
0
V
ITH
(V)
1.0
2.0
3.0
0.5
1.5
2.5
20 40 60 80
1538/39 • G06
10010030507090
Burst Mode
OPERATION
CONTINUOUS/
Adaptive Power 
MODE
EXTV
CC
Switch Drop
vs INTV
CC
Load Current
Input Supply Current
vs Input Voltage
INTV
CC
Regulation
vs INTV
CC
Load Current
INPUT VOLTAGE (V)
0
0
SUPPLY CURRENT (mA)
0.5
1.0
1.5
2.0
2.5
0
5V STANDBY CURRENT (µA)
20
40
60
80
100
5
10 15 20
LTC1538/39 • TPC07
25 30
5V, 3.3V OFF
5V STANDBY
5V, 3.3V ON
5V OFF, 3.3V ON
5V ON, 3.3V OFF
INTV
CC
LOAD CURRENT (mA)
0
INTV
CC
PERCENT CHANGE, NORMALIZED (V)
0
1
5040
1538/39 • G08
–1
–2
10
20
30
2
70°C
25°C
EXTV
CC
= 0V
INTV
CC
LOAD CURRENT (mA)
0
EXTV
CC
– INTV
CC
(mV)
200
300
20
1538/39 • G09
100
0
5
10
15
25 30
–45°C
25°C
70°C
6
LTC1538-AUX/LTC1539
TYPICAL PERFORMANCE CHARACTERISTICS
U
W
SFB1 Pin Current vs
Temperature
Normalized Oscillator Frequency
vs Temperature
TEMPERATURE (°C)
–40
FREQUENCY (%)
5
10
35 85
1538/39 • G10
f
O
–15 10
60 110 135
–5
–10
TEMPERATURE (°C)
–40
SFB CURRENT (µA)
–1.50
0.25
0
35 85
1538/39 • G12
0.75
–1.00
–15 10
60 110 135
–1.25
–1.50
Transient Response
TEMPERATURE (°C)
–40
146
CURRENT SENSE THRESHOLD (mV)
148
150
152
154
–15 10 35 60
1538/39 • G13
85 110 135
Auxiliary Regulator Load
Regulation
AUXILIARY LOAD CURRENT (mA)
0
AUXILIARY OUTPUT VOLTAGE (V)
12.0
12.1
12.2
160
1538/39 • G18
11.9
11.8
11.7
40
80
120
200
EXTERNAL PNP: 2N2907A
V
OUT
50mV/DIV
I
LOAD
= 1A to 3A
1538/39 • G15
RUN/SS Pin Current vs
Temperature
TEMPERATURE (°C)
–40
0
RUN/SS CURRENT (µA)
1
2
3
4
–15 10 35 60
1538/39 • G11
85 110 135
Transient Response
Soft Start: Load Current vs Time
V
OUT
50mV/DIV
I
LOAD
= 50mA to 1A
1538/39 • G14
1538/39 • G17
Burst Mode Operation
V
OUT
20mV/DIV
V
OUT
200mV/DIV
I
LOAD
= 50mA
1538/39 • G16
RUN/SS
5V/DIV
INDUCTOR
CURRENT
1A/DIV
Maximum Current Comparator
Threshold Voltage vs Temp
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