LTC1628/LTC1628-PG
High Efficiency, 2-Phase
Synchronous Step-Down Switching Regulators
FEATURES DESCRIPTIO
n
Out-of-Phase Controllers Reduce Required Input The LTC 1628/LTC1628-PG are high performance dual
Capacitance and Power Supply Induced Noise step-down switching regulator controllers that drive all
n
OPTI-LOOP Compensation Minimizes C N-channel synchronous power MOSFET stages. A con-
OUT
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1% Output Voltage Accuracy stant frequency current mode architecture allows adjust-
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Dual N-Channel MOSFET Synchronous Drive ment of the frequency up to 300kHz. Power loss and noise
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Power Good Output Voltage Monitor (LTC1628-PG) due to the ESR of the input capacitors are minimized by
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DC Programmed Fixed Frequency 150kHz to 300kHz operating the two controller output stages out of phase.
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Wide V Range: 3.5V to 36V Operation
IN
OPTI-LOOP compensation allows the transient response
n
Very Low Dropout Operation: 99% Duty Cycle
to be optimized over a wide range of output capacitance and
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Adjustable Soft-Start Current Ramping
ESR values. The precision 0.8V reference and power good
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Foldback Output Current Limiting
output indicator are compatible with future microproces-
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Latched Short-Circuit Shutdown with Defeat Option
sor generations, and a wide 3.5V to 30V (36V maximum)
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Output Overvoltage Protection
input supply range encompasses all battery chemistries.
n
Remote Output Voltage Sense
n A RUN/SS pin for each controller provides both soft-start
Low Shutdown I : 20m A
Q
n and optional timed, short-circuit shutdown. Current
5V and 3.3V Standby Regulators
n foldback limits MOSFET dissipation during short-circuit
Selectable Constant Frequency or Burst Mode
conditions when overcurrent latchoff is disabled. Output
Operation
n overvoltage protection circuitry latches on the bottom
Available in 5mm 5mm QFN and
MOSFET until V returns to normal. The FCB mode pin
28-Pin SSOP Packages OUT
U can select among Burst Mode, constant frequency mode
APPLICATIO S
and continuous inductor current mode or regulate a
secondary winding. The LTC1628-PG includes a power
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Notebook and Palmtop Computers, PDAs
good output pin that replaces the FLTCPL, fault coupling
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Battery Chargers
control pin of the LTC1628.
n
Portable Instruments
, LTC and LT are registered trademarks of Linear Technology Corporation.
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Battery-Operated Digital Devices
OPTI-LOOP and Burst Mode are registered trademarks of Linear Technology Corporation.
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DC Power Distribution Systems
V
IN
5.2V TO 28V
C
IN
+
TYPICAL APPLICATIO
1F
22F
4.7F
D3
CERAMIC
D4 50V
V INTV
IN CC
CERAMIC
M1 M3
TG1 TG2
L1 L2
C , 0.1F C , 0.1F
B1 B2
6.3H BOOST1 BOOST2 6.3H
SW1 SW2
LTC1628
M2 M4
BG1 BG2
D1 D2
SGND PGND
+ +
SENSE1 SENSE2
R R
SENSE1 1000pF SENSE2
1000pF
0.01 0.01
V SENSE1 SENSE2 V
OUT1 OUT2
5V V V 3.3V
OSENSE1 OSENSE2
5A 5A
R2 R4
I I
TH1 TH2
105k
C C 63.4k
C C1 C2 C
OUT1
OUT
+ R1 RUN/SS1 RUN/SS2 R3
1% 220pF 220pF 1%
47F
56F
20k 20k
R R
6V C1 C C C2 6V
SS1 SS2
1% 1%
15k 15k
SP
0.1F 0.1F SP
M1, M2, M3, M4: FDS6680A
1628 F01
Figure 1. High Efficiency Dual 5V/3.3V Step-Down Converter
1628fb
1
+
U
ULTC1628/LTC1628-PG
ABSOLUTE AXI U RATI GS (Note 1)
Input Supply Voltage (V ).........................36V to 0.3V I I , V , V Voltages ...2.7V to 0.3V
TH1, TH2 OSENSE1 OSENSE2
IN
Top Side Driver Voltages Peak Output Current <10m s (TG1, TG2, BG1, BG2) ... 3A
(BOOST1, BOOST2) ...................................42V to 0.3V INTV Peak Output Current ................................ 50mA
CC
Switch Voltage (SW1, SW2) .........................36V to 5V Operating Temperature Range
INTV EXTV , RUN/SS1, RUN/SS2, (BOOST1-SW1), LTC1628C/LTC1628C-PG ........................ 0 C to 85 C
CC, CC
(BOOST2-SW2), PGOOD .............................7V to 0.3V LTC1628I/LTC1628I-PG ..................... 40 C to 85 C
+ +
SENSE1 , SENSE2 , SENSE1 , Junction Temperature (Note 2)............................. 125 C
SENSE2 Voltages ........................ (1.1)INTV to 0.3V Storage Temperature Range ................. 65 C to 150 C
CC
FREQSET, STBYMD, FCB, Lead Temperature (Soldering, 10 sec)
FLTCPL Voltage ................................... INTV to 0.3V (G Package Only) .................................................. 300 C
CC
UUW
PACKAGE/ORDER I FOR ATIO
TOP VIEW
TOP VIEW ORDER PART ORDER PART
NUMBER NUMBER
1 28 FLTCPL*
RUN/SS1
+
2 27 TG1
SENSE1
LTC1628CG LTC1628CUH
32 31 30 29 28 27 26 25
3 26 SW1
SENSE1
LTC1628IG V 1 24 BOOST1 LTC1628IUH
OSENSE1
4 25 BOOST1
V
OSENSE1
FREQSET 2 23 V
LTC1628CG-PG IN
5 24 V
FREQSET
IN
STBYMD 3 22 BG1
LTC1628IG-PG
6 23 BG1
STBYMD
FCB 4 21 EXTV
CC
7 22 EXTV
FCB
CC
I 5 20 INTV
TH1 CC
8 21 INTV
I
TH1 CC
SGND 6 19 PGND
9 20 PGND
SGND
3.3V 7 18 BG2
OUT
UH PART
10 19 BG2
3.3V
OUT
I 8 17 BOOST2
TH2
MARKING
11 18 BOOST2
I
TH2
9 10 11 12 13 14 15 16
12 17 SW2
V
OSENSE2
1628
13 16 TG2
SENSE2
1628I
+
14 15 RUN/SS2
SENSE2
UH PACKAGE
G PACKAGE 32-LEAD (5mm 5mm) PLASTIC QFN
28-LEAD PLASTIC SSOP
q = 34 C/W
JA
T = 125 C, q = 95 C/W
JMAX JA
EXPOSED PAD IS SGND
(MUST BE SOLDERED TO PCB)
*PGOOD ON THE LTC1628-PG
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25 C. V = 15V, V = 5V unless otherwise noted.
A IN RUN/SS1, 2
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loops
V Regulated Feedback Voltage (Note 3); I Voltage = 1.2V l 0.792 0.800 0.808 V
OSENSE1, 2 TH1, 2
I Feedback Current (Note 3) 5 50 nA
VOSENSE1, 2
V Reference Voltage Line Regulation V = 3.6V to 30V (Note 3) 0.002 0.02 %/V
REFLNREG IN
V Output Voltage Load Regulation (Note 3)
LOADREG
Measured in Servo Loop; D I Voltage = 1.2V to 0.7V l 0.1 0.5 %
TH
Measured in Servo Loop; D I Voltage = 1.2V to 2.0V l 0.1 0.5 %
TH
1628fb
2
V NC
OSENSE2
NC SENSE1
+
SENSE2 SENSE1
+
SENSE2 NC
RUN/SS2 RUN/SS1
TG2 FLTCPL
SW2 TG1
NC SW1
U WWW