LTC3735 Datasheet, PDF (1/32 Pages) Linear Technology – 2-Phase, High Efficiency DC/DC Controller for Intel Mobile CPUs

FEATURES
n _{Output Stages Operate Antiphase}
n _{±1% Output Voltage Accuracy}
n _{6-Bit IMVP-IV VID Code: VOUT = 0.7V to 1.708V}
n _{Intel Compatible Power Saving Mode (PSIB)}
n _{Stage Shedding Improves Low Current Efficiency}
n _{Power Good Output with Adaptive Masking}
n _{Lossless Voltage Positioning}
n _{Dual Input Supply Capability for Load Sharing}
n _{Resistor Programmable VOUT at Boot-Up and Deeper}
Sleep State
n _{Resistor Programmable Deep Sleep Offset}
n _{Programmable Fixed Frequency: 210kHz to 550kHz}
n _{Adjustable Soft-Start Current Ramping}
n _{Foldback Output Current Limit}
n _{Short-Circuit Shutdown Timer with Defeat Option}
n _{Overvoltage Protection}
n _{Available in 36-Lead SSOP (0.209 Wide) and 38-Lead}
(5mm × 7mm) Packages
APPLICATIONS
n _{Mobile and Desktop Computers}
n _{Internet Servers}
LTC3735
2-Phase, High Efficiency
DC/DC Controller for
Intel Mobile CPUs
DESCRIPTION
The LTC^®3735 is a 2-phase synchronous step-down
switching regulator controller that drives all N-channel
power MOSFETs in a constant frequency architecture. The
output voltage is programmable by six VID bits during
normal operation and by external resistors during initial
boot-up and deeper sleep state. The LTC3735 drives its two
output stages out-of-phase at frequencies up to 550kHz
to minimize the RMS ripple currents in both input and
output capacitors. This antiphase technique also doubles
the apparent switching frequency, improving the transient
response while operating each phase at an optimum fre-
quency for efficiency. Thermal design is further simplified
by cycle-by-cycle current sharing between the two phases.
An Intel compatible PSIB input is provided to select between
two modes of operation. Fully enhanced synchronous
mode achieves a very small output ripple and very fast
transient response while power saving mode realizes
very high efficiency. OPTI-LOOP^® compensation allows
the transient response to be optimized for a wide range
of output capacitance and ESR values.
L, LT, LTC, LTM, OPTI-LOOP, PolyPhase, Linear Technology and the Linear logo are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
TYPICAL APPLICATION
100pF
232k
V_OA⁺
R_C
4.74k
C_C
470pF
0.1µF
MCH_PG TG1
DPRSLPVR
STP_CPUB
SW1
PSIB
FREQSET
BG1
VID5-VID0 ^PGND
PGOOD
I_TH
SSEENNSSEE11^+–
RUN/SS
TG2
SW2
SGND
BG2
LTC3735
M1
1µH
M2 D1
M3
1µH
M4
D2
4.5V TO 7V
4.7µF
BAT54A
0.47µF
0.47µF
SW2 SW1
PV_CC
SSEENNSSEE22^+–
RBOOT
BOOST1 RDPRSLP
BOOST2 _RDPVSOLAP+
OAOUT
V_OA–
13.3k
12.7k
56.2k
1.27M
13.3k
549k ^VOA+
3735 F01
0.002Ω
0.002Ω
V_IN
5V TO 24V
V_OUT
0.7V TO 1.708V
+ ^{COUT 40A}
C_IN
330µF
10µF
2V
35V
×5
×4
Figure 1. High Current 2-Phase Step-Down Converter
3735fa
1