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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.

1
LTC1538-AUX/LTC1539
Dual High Efficiency,
Low Noise, Synchronous
Step-Down Switching Regulators
Figure 1. High Efficiency Dual 5V/3V Step-Down Converter
BOOST 2BOOST 1
TGL2
TGS2
SW2
BG2
SENSE
+
2
SENSE
2
V
OSENSE2
I
TH2
TGL1
M3*
M1
M2
TGS1
D1
MBR140T3
V
OUT1
5V
3.5A
V
OUT2
3.3V
3.5A
L1
10µH
SW1
BG1 LTC1539
SENSE
+
1
SENSE
1
C
SS1
0.1µF
C
C1
1000pF
C
OUT1
220µF
10V
R
SENSE1
0.03
R
SENSE2
0.03
C
OUT
220µF
10V
R
C1
10k
I
TH1
RUN/SS2PGNDSGNDV
PROG2
C
DSC
INTV
CC
D
B2
, CMDSH-3D
B1
, CMDSH-3
V
IN
V
PROG1
RUN/SS1
D2
MBR140T3
C
B1 
0.1µF
C
B2
,
0.1µF
4.7µF
16V
M6*
1538 F01
M4
1000pF
1000pF
C
OSC
56pF
C
SS2
0.1µF
C
C1A
220pF
M1, M2, M4, M5: Si4412DY M3, M6: IRLML2803 *NOT REQUIRED FOR LTC1538-AUX
C
C2A
470pF
C
C2
1000pF
R
C2
10k
+
L2
10µH
V
IN
5.2V TO 28V
5V STANDBY
+
+
C
IN
22µF
35V
× 4
+
BOLD LINES INDICATE HIGH CURRENT PATHS
M5
TYPICAL APPLICATION
U
Maintains Constant Frequency at Low Output Currents
Dual N-Channel MOSFET Synchronous Drive
Programmable Fixed Frequency (PLL Lockable)
Wide V
IN
Range: 3.5V to 36V Operation
Ultrahigh Efficiency
Very Low Dropout Operation: 99% Duty Cycle
Low Dropout, 0.5A Linear Regulator for VPP
Generation or Low Noise Audio Supply
Built-In Power-On Reset Timer
Programmable Soft Start
Low-Battery Detector
Remote Output Voltage Sense
Foldback Current Limiting (Optional)
Pin Selectable Output Voltage
5V Standby Regulator Active in Shutdown: I
Q
< 200µA
Output Voltages from 1.19V to 9V
Available in 28- and 36-Lead SSOP Packages
The LTC
®
1538-AUX/LTC1539 are dual, synchronous step-
down switching regulator controllers which drive external
N-channel power MOSFETs in a phase-lockable fixed
frequency architecture. The Adaptive Power
TM
output stage
selectively drives two N-channel MOSFETs at frequencies
up to 400kHz while reducing switching losses to maintain
high efficiencies at low output currents.
An auxiliary 0.5A linear regulator using an external PNP
pass device provides a low noise, low dropout voltage
source. A secondary winding feedback control pin (SFB1)
guarantees regulation regardless of load on the main
output by forcing continuous operation.
A 5V/20mA regulator, internal 1.19V reference and an
uncommitted comparator remain active when both con-
trollers are shut down. A power-on reset timer (POR) is
included which generates a signal delayed by 65536/f
CLK
(typ 300ms) after the controller’s output is within 5% of
the regulated first voltage. Internal resistive dividers pro-
vide pin selectable output voltages with remote sense
capability on one of the two outputs.
The operating current levels are user-programmable via
external current sense resistors. Wide input supply range
allows operation from 3.5V to 30V (36V maximum).
FEATURES
DESCRIPTION
U
, LTC and LT are registered trademarks of Linear Technology Corporation.
Adaptive Power is a trademark of Linear Technology Corporation.
Notebook and Palmtop Computers, PDAs
Portable Instruments
Battery-Operated Devices
DC Power Distribution Systems
APPLICATIONS
U
2
LTC1538-AUX/LTC1539
ABSOLUTE MAXIMUM RATINGS
W
WW
U
Input Supply Voltage (V
IN
)....................... 36V to –0.3V
Topside Driver Voltage (BOOST 1, 2) ...... 42V to –0.3V
Peak Switch Voltage > 10µs (SW 1, 2) ... V
IN
+ 5V to –5V
EXTV
CC
Voltage........................................ 10V to –0.3V
POR1, LBO Voltages................................ 12V to –0.3V
AUXFB Voltage ........................................ 20V to –0.3V
AUXDR Voltage........................................ 28V to –0.3V
SENSE
+
1, SENSE
+
2, SENSE
1, SENSE
2,
V
OSENSE2
Voltages ................... INTV
CC
+ 0.3V to –0.3V
V
PROG1
, V
PROG2
Voltages.................... INTV
CC
to –0.3V
PLL LPF, I
TH1
, I
TH2
Voltages................... 2.7V to –0.3V
AUXON, PLLIN, SFB1,
RUN/SS1, RUN/SS2, LBI, Voltages ......... 10V to –0.3V
Peak Output Current < 10µs (TGL1, 2, BG1, 2)......... 2A
Peak Output Current < 10µs (TGS1, 2) .............. 250mA
INTV
CC
Output Current ........................................ 50mA
Operating Temperature Range
LTC1538-AUXCG/LTC1539CGW............ O°C to 70°C
LTC1538-AUXIG/LTC1539IGW.......... –40°C to 85°C
Junction Temperature (Note 1)............................125°C
Storage Temperature Range ................ –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................300°C
PACKAGE/ORDER INFORMATION
W
U
U
ORDER
PART NUMBER
LTC1538CG-AUX
LTC1538IG-AUX
ORDER
PART NUMBER
LTC1539CGW
LTC1539IGW
T
JMAX
= 125°C, θ
JA
= 95°C/W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
TOP VIEW
G PACKAGE
28-LEAD PLASTIC SSOP
28
27
26
25
24
23
22
21
20
19
18
17
16
15
BOOST 1
RUN/SS1
SENSE
+
1
SENSE
1
V
PROG1
I
TH1
C
OSC
SGND
SFB1
I
TH2
V
OSENSE2
SENSE
2
SENSE
+
2
RUN/SS2
TGL1
SW1
V
IN
BG1
INTV
CC
/5V
PGND
BG2
EXTV
CC
SW2
TGL2
BOOST 2
AUXON
AUXFB
AUXDR
T
JMAX
= 125°C, θ
JA
= 85°C/W
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TOP VIEW
GW PACKAGE
36-LEAD PLASTIC SSOP
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
RUN/SS1
SENSE
+
1
SENSE
1
V
PROG1
I
TH1
POR1
C
OSC
SGND
LBI
LBO
SFB1
I
TH2
V
PROG2
V
OSENSE2
SENSE
2
SENSE
+
2
RUN/SS2
AUXDR
PLL LPF
PLLIN
BOOST 1
TGL1
SW1
TGS1
V
IN
BG1
INTV
CC
/5V
PGND
BG2
EXTV
CC
TGS2
SW2
TGL2
BOOST 2
AUXON
AUXFB
Consult factory for Military grade parts.
3
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
Main Control Loops
I
IN
V
OSENSE2
Feedback Current V
PROG1,
V
PROG2
Pins Open (Note 2) 10 50 nA
V
OUT1,2
Regulated Output Voltage (Note 2)
1.19V (Adjustable) Selected V
PROG1,
V
PROG2
Pins Open 1.178 1.19 1.202 V
3.3V Selected V
PROG1,
V
PROG2
= 0V 3.220 3.30 3.380 V
5V Selected V
PROG1,
V
PROG2
= INTV
CC
4.900 5.00 5.100 V
V
LINEREG1,2
Reference Voltage Line Regulation V
IN
= 3.6V to 20V (Note 2), V
PROG1,2
Pins Open 0.002 0.01 %/V
V
LOADREG1,2
Output Voltage Load Regulation I
TH1,2
Sinking 5µA (Note 2) 0.5 0.8 %
I
TH1,2
Sourcing 5µA 0.5 0.8 %
V
SFB1
Secondary Feedback Threshold V
SFB1
Ramping Negative 1.16 1.19 1.22 V
I
SFB1
Secondary Feedback Current V
SFB1
= 1.5V 1 2 µA
V
OVL
Output Overvoltage Lockout V
PROG1,2
Pin Open, SENSE
1
and V
OSENSE2
Pins 1.24 1.28 1.32 V
I
PROG1,2
V
PROG1,2
Input Current 0.5V > V
PROG1,2
–3 6 µA
INTV
CC
– 0.5V < V
PROG1,2
< INTV
CC
3 6 µA
I
Q
Input DC Supply Current EXTV
CC
= 5V (Note 3)
Normal Mode 3.6V < V
IN
< 30V, V
AUXON
= 0V 320 µA
Shutdown V
RUN/SS1,2
= 0V, 3.6V < V
IN
< 15V 70 200 µA
V
RUN/SS1,2
Run Pin Threshold 0.8 1.3 2 V
I
RUN/SS1,2
Soft Start Current Source V
RUN/SS1,2
= 0V 1.5 3 4.5 µA
V
SENSE(MAX)
Maximum Current Sense Threshold V
OSENSE1,2
= 0V, 5V V
PROG1,2
= Pins Open 130 150 180 mV
TGL1, 2 t
r
, t
f
TGL1, TGL2 Transition Time
Rise Time C
LOAD
= 3000pF 50 150 ns
Fall Time C
LOAD
= 3000pF 50 150 ns
TGS1, 2 t
r
, t
f
TGS1, TGS2 Transition Time
Rise Time C
LOAD
= 500pF 100 150 ns
Fall Time C
LOAD
= 500pF 50 150 ns
BG1, 2 t
r
, t
f
BG1, BG2 Transition Time
Rise Time C
LOAD
= 3000pF 50 150 ns
Fall Time C
LOAD
= 3000pF 50 150 ns
Internal V
CC
Regulator –5V Standby
V
INTVCC
Internal V
CC
Voltage 6V < V
IN
< 30V, V
EXTVCC
= 4V 4.8 5.0 5.2 V
V
LDO
INT INTV
CC
Load Regulation INTV
CC
= 20mA, V
EXTVCC
= 4V 0.2 1 %
V
LDO
EXT EXTV
CC
Voltage Drop INTV
CC
= 20mA, V
EXTVCC
= 5V 170 300 mV
V
EXTVCC
EXTV
CC
Switchover Voltage INTV
CC
= 20mA, EXTV
CC
Ramping Positive 4.5 4.7 V
Oscillator and Phase-Locked Loop
f
OSC
Oscillator Frequency C
OSC
= 100pF, LTC1539: PLL LPF = 0V (Note 4) 112 125 138 kHz
VCO High LTC1539, V
PLLLPF
= 2.4V 200 240 kHz
R
PLLIN
PLLIN
Input Resistance 50 k
I
PLLLPF
Phase Detector Output Current LTC1539
Sinking Capability f
PLLIN
< f
OSC
10 15 20 µA
Sourcing Capability f
PLLIN
> f
OSC
10 15 20 µA
Power-On Reset
V
SATPOR1
POR1 Saturation Voltage I
POR1
= 1.6mA, V
OSENSE1
= 1V, 0.6 1 V
V
PROG1
Pins Open
I
LPOR1
POR1 Leakage V
POR1
= 12V, V
OSENSE1
= 1.19V, V
PROG1
Pin Open 0.2 1 µA
V
THPOR1
POR1 Trip Voltage V
PROG1
Pin Open % of V
REF
V
OSENSE1
Ramping Negative 11 7.5 4 %
t
DPOR1
POR1 Delay V
PROG1
Pin Open 65536 Cycles
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