LTC3714_15 Datasheet, PDF (1/28 Pages) Linear Technology – Intel Compatible, Wide Operating Range, Step-Down Controller with Internal Op Amp

LTC3714
Intel Compatible,
Wide Operating Range, Step-Down Controller
with Internal Op Amp
Features
n _{True Current Mode with Ultrafast Transient Response}
n _{Stable with Ceramic COUT}
n _{tON(MIN) < 100ns for Operation from High Input}
Ranges
n _{Supports Active Voltage Positioning}
n _{No Sense Resistor Required}
n _{5-Bit VID Programmable Output Voltage: 0.6V to 1.75V}
n _{Dual N-Channel MOSFET Synchronous Drive}
n _{Programmable Output Offsets}
n _{Power Good Output Voltage Monitor}
n _{Wide VIN Range: 4V to 36V}
n _{±1% 0.6V Reference}
n _{Adjustable Frequency}
n _{Programmable Soft-Start}
n _{Output Overvoltage Protection}
n _{Optional Short-Circuit Shutdown Timer}
n _{Forced Continuous Control Pin}
n _{Logic Controlled Micropower Shutdown: IQ ≤ 30µA}
n _{Available in 0.209" Wide 28-Lead SSOP Package}
Applications
n _{Power Supply for Mobile Pentium}^® _{Processors and}
Transmeta Processors
n _{Notebook and Portable Computers}
Description
The LTC^®3714 is a synchronous step-down switching
regulator controller for CPU power. An output voltage
between 0.6V and 1.75V is selected by a 5-bit code (Intel
mobile VID specification). The controller uses a constant
on-time, valley current control architecture to deliver very
low duty cycles without requiring a sense resistor. Oper-
ating frequency is selected by an external resistor and is
compensated for variations in V_IN and V_OUT.
Discontinuous mode operation provides high efficiency
operation at light loads. A forced continuous control pin
reduces noise and RF interference and can assist second-
ary winding regulation by disabling discontinuous mode
when the main output is lightly loaded. Internal op amp
allows programmable offsets to the output voltage during
power saving modes.
Fault protection is provided by internal foldback current
limiting, an output overvoltage comparator and optional
short-circuit shutdown timer. Soft-start capability for
supply sequencing is accomplished using an external
timing capacitor. The regulator current limit level is user
programmable. Wide supply range allows operation from
4V to 36V at the input.
L, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
Typical Application
INTV_CC
C_SS
0.1µF
C_C ^RC
5-BIT
VID
LTC3714
PGOOD I_ON
V_IN
RUN/SS TG
I_TH
SW
BOOST
SGND
INTV_CC
VID4
BG
VID3 _SENSE
VID2
VID1
VID0 _PGND
R_ON
C_B, 0.22µF
D_B
CMDSH-3
+ _CVCC
4.7µF
M1
IRF7811 L1
×2 0.68µH
M2
IRF7811
×3
0.003Ω*
D1*
UPS840
Transient Response of 8A to 23A Output Load Step
V_IN
10µF ^{5V TO 24V}
35V
×4
V_OUT
0.6V TO 1.75V
+ ^{COUT 23A}
270µF
2V
×4
1.395V
V_OUT
1.35V
50mV/DIV
1.213V
23A
I_LOAD
10A/DIV
8A
V_OSENSE
3714 F01
*OPTIONAL
Figure 1. High Efficiency Step-Down Converter
20µs/DIV
3714 TA03
3714f
1