1
LTC1702
1702fa
Dual 550kHz Synchronous
2-Phase Switching Regulator Controller
The LTC
®
1702 is a dual switching regulator controller opti-
mized for high efficiency with low input voltages. It includes
two complete, on-chip, independent switching regulator
controllers each designed to drive a pair of external N-channel
MOSFET devices in a voltage mode feedback, synchronous
buck configuration. The LTC1702 uses a constant-frequency,
true PWM design switching at 550kHz, minimizing external
component size and cost and maximizing load transient
performance. The synchronous buck architecture automati-
cally shifts to discontinuous and then to Burst Mode
TM
operation as the output load decreases, ensuring maximum
efficiency over a wide range of load currents.
The LTC1702 features an onboard reference trimmed to
0.5% and can provide better than 1% regulation at the
converter outputs. Open-drain logic outputs indicate whether
either output has risen to within 5% of the final output voltage
and an optional latching FAULT mode protects the load if the
output rises 15% above the intended voltage. Each channel
can be enabled independently; with both channels disabled,
the LTC1702 shuts down and supply current drops below
100µA.
■
Two Independent Controllers in One Package
■
Two Sides Run Out-of-Phase to Minimize C
IN
■
All N-Channel External MOSFET Architecture
■
No External Current Sense Resistors
■
Excellent Output Regulation: 1% Total Output
Accuracy
■
550kHz Switching Frequency Minimizes External
Component Size
■
1A to 25A Output Current per Channel
■
High Efficiency over Wide Load Current Range
■
Quiescent Current Drops Below 100µA in Shutdown
■
Small 24-Pin Narrow SSOP Package
■
Microprocessor Core and I/O Supplies
■
Multiple Logic Supply Generator
■
Distributed Power Applications
■
High Efficiency Power Conversion
Dual Output High Power 3.3V/2.5V Logic Supply
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
LTC1702
PV
CC
BOOST1
BG1
TG1
SW1
I
MAX1
PGOOD1
FCB
RUN/SS
COMP1
SGND
FB1
I
MAX2
BOOST2
BG2
TG2
SW2
PGND
PGOOD2
FAULT
RUN/SS2
COMP2
FB2
V
CC
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
1µF
10Ω
1µF
1µF
27k
27k
1.6k
68k
1702 TA01
V
IN
1.2k
10k
1%
C
OUT1
180µF
×4
820pF
27pF
680pF
47k
1µF
V
OUT1
2.5V
AT 15A
1µF
4.75k
1%
Q2Q1
Q4Q3
D3
D2
C
OUT1
, C
OUT2
: PANASONIC EEFUE0G181R
C
IN
: KEMET TS10X337M010AS
D1, D2: MOTOROLA MBR0520LT1
D3, D4: MOTOROLA MBRS320T3
L1, L2: SUMIDA CEP125-1R0
Q1 TO Q8: FAIRCHILD FDS6670A
D1
PWRGD1
L1
1µH
+
10µF
10µF
1µF
V
IN
= 5V ±10%
1µF
C
IN
330µF
×3
+
Q7
Q5
Q8
Q6
D4
680pF
27pF
3300pF
15.8k
1%
4.99k
1%
10k
L2
1µH
C
OUT2
180µF
×4
1µF
V
OUT2
3.3V/15A
PWRGD2
FAULT
+
V
IN
10k
, LTC and LT are registered trademarks of Linear Technology Corporation. Burst Mode
is a registered trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents including 5481178,
5847554, 6304066, 6307356, 6580258.