LTC1703_15 Datasheet, PDF (1/36 Pages) Linear Technology – Dual 550kHz Synchronous 2-Phase Switching Regulator Controller with 5-Bit VID

LTC1703
Dual 550kHz Synchronous
2-Phase Switching Regulator
Controller with 5-Bit VID
FEATURES
■ _{Side 1 Output Is Compliant with Intel Mobile}
VID Specifications (Includes 5-Bit DAC)
■ _{0.9V to 2.0V Output Voltage with 25mV/50mV Steps}
■ _{Two Sides Run Out-of-Phase to Minimize CIN}
■ _{Precision Internal 0.8V ±1% Reference}
■ _{Two Independent PWM Controllers in One Package}
■ _{All N-Channel External MOSFET Architecture}
■ _{No External Current Sense Resistor}
■ _{550kHz Switching Frequency Minimizes External}
Component Size
■ _{Very Fast Transient Response}
■ _{Up to 25A Output Current per Channel}
■ _{Low Shutdown Current: < 100µA}
■ _{Small 28-Pin SSOP Package}
U
APPLICATIO S
■ _{Mobile Pentium}^® _{III Processor Systems}
■ _{Microprocessor Core and I/O Supplies}
■ _{Multiple Logic Supply Generator}
■ _{High Efficiency Power Conversion}
, 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.
DESCRIPTIO
The LTC^®1703 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 is designed to drive a pair of external
N-channel MOSFET devices in a voltage mode feedback,
synchronous buck configuration. The LTC1703 includes
digital output voltage adjustment on side 1 that conforms to
the Intel Mobile VID specification. It uses a constant-
frequency, true PWM design switching at 550kHz, minimiz-
ing external component size and cost and optimizing load
transient performance. The synchronous buck architecture
automatically shifts to discontinuous and then to Burst
Mode^® operation as the output load decreases, ensuring
maximum efficiency over a wide range of load currents.
The LTC1703 features an onboard reference trimmed to 1%
and delivers better than 1.5% regulation at the converter
outputs. 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 LTC1703 shuts down and supply current drops
below 100µA.
TYPICAL APPLICATIO
Dual Output Mobile Pentium III Processor Supply
V_OUT1
0.9V
TO 2V
15A
GND
DCP1
MBR0520LT1
L1
QT1
1µH
1µF
DCP2
MBR0520LT1
LTC1703
+ ^COUT1
180µF
QB1A
QB1B
CCP1
1µF
1
2
PV_CC
BOOST1
3 _BG1
I_MAX2
BOOST2
28
27
BG2 ²⁶
4V
×6
4 _TG1
5 _SW1
TG2 ²⁵
SW2 ²⁴
R_IMAX1,18.7k
6
7
I_MAX1
FCB
PGND ²³
FAULT ²²
8 _{RUN/SS1 RUN/SS2} 21
C_SS1
9 _COMP1
COMP2 ²⁰
0.22µF
R21
100k
C31
220pF
C21
C11
220pF
15pF
R31, 10k
10 _SGND
11 _FB1
12 _SENSE
13 _VID0
14 _VID1
FB2 ¹⁹
V_CC
VID4
18
17
VID3 ¹⁶
VID2 ¹⁵
L1: MURATA LQT12535C1R5N12
L2: COILTRONICS UP2B-2R2
QT1, QB1A, QB1B: INTERNATIONAL RECTIFIER IRF7811
QT2, QB2: 1/2 FAIRCHILD NDS8926
VID0
VID1
VID2
VID3
VID4
QT2
L2
2.2µH
CCP2
1µF
+
QB2
R_IMAX2
20k
R22, 100k
C22
15pF
C12
220pF
1µF
+ C_IN
150µF
10V
×2
V_IN
4.5V TO 5.5V
C_OUT2
180µF
4V
R12
10.2k
0.1%
C32
2200pF
R32
1k
10Ω
V_OUT2
1.5V
3A
RB2
11.5k
0.1%
GND
GND
C_SS2
0.22µF
1703 TA01
1703fa
1