19-2010; Rev 0; 4/01
Dynamically-Adjustable, Synchronous Step-Down
Controller with Integrated Voltage Positioning
General Description
The MAX1813 step-down controller is intended for core
CPU DC-DC converters in notebook computers. The
controller features a dynamically adjustable output (5-
bit DAC), ultra-fast transient response, high DC accura-
cy, and high efficiency necessary for leading-edge
CPU core power supplies. Maxim’s proprietary Quick-
PWM™ quick-response, constant-on-time PWM control
scheme handles wide input/output voltage ratios with
ease and provides 100ns “instant-on” response to load
transients while maintaining a relatively constant switch-
ing frequency.
The MAX1813 is designed specifically for CPU core
applications requiring a voltage-positioned supply. The
voltage-positioning input (VPCS), combined with a
high-DC-accuracy control loop, is used to implement a
power supply that modifies its output set point in
response to the load current. This arrangement
decreases full-load power dissipation and reduces the
required number of output capacitors.
The output voltage can be dynamically adjusted
through the 5-bit digital-to-analog converter (DAC)
inputs over a 0.600V to 2V range. The MAX1813
includes an internal multiplexer that selects between
three different DAC code settings. The first two inputs
are controlled by five digital input pins (D0–D4). The
third input is used for the suspend mode and controlled
by two 4-level input pins (S0, S1). Output voltage transi-
tions are accomplished with a proprietary precision
slew-rate control that minimizes surge currents to and
from the battery while guaranteeing “just-in-time” arrival
at the new DAC setting.
The MAX1813’s 28V input range enables single-stage
buck conversion from high-voltage batteries for the
maximum possible efficiency. Alternatively, the con-
troller’s high-frequency capability combined with two-
stage conversion (stepping down the +5V system
supply instead of the battery) allows the smallest possi-
ble physical size.
The MAX1813 is available in a 28-pin QSOP package.
Applications
Notebook Computers
(Intel IMVP–II™/Coppermine™)
Docking Stations
CPU Core Supply
Single-Stage (BATT to VCORE) Converters
Two-Stage (+5V to VCORE) Converters
Typical Operating Circuit appears at end of data sheet.
Features
o High-Efficiency Voltage Positioning
o Quick-PWM Architecture
o ±1% VOUT Accuracy Over Line
o Adjustable Output Slew Rate
o 0.600V to 2V Adjustable Output Range (5-Bit DAC)
o 2V to 28V Battery Input Range
o 200/300/600/1000kHz Switching Frequency
o Output Undervoltage and Overvoltage Protection
o Drives Large Synchronous-Rectifier MOSFETs
o ±20% Accurate Current-Limit
o 10µA Shutdown Supply Current
o 2V ±1% Reference Output
o Power-Good (PGOOD) Indicator
o Small 28-Pin QSOP Package
PART
MAX1813EEI
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
28 QSOP
Pin Configuration
TOP VIEW
V+ 1
VPCS 2
SKP/SDN 3
TIME 4
FB 5
CC 6
S0 7
S1 8
VCC 9
TON 10
REF 11
ILIM 12
PGOOD 13
GND 14
MAX1813
QSOP
28 DH
27 LX
26 BST
25 D0
24 D1
23 D2
22 D3
21 D4
20 CODE
19 ZMODE
18 SUS
17 VDD
16 DL
15 PGND
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
Coppermine and IMVP-ΙΙ are trademarks of Intel Corp.
________________________________________________________________ Maxim Integrated Products 1
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
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