19-1636; Rev 0; 1/00
KIT
ATION
EVALU
BLE
AVAILA
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
General Description
Features
o
Quick-PWM Architecture
o
±1% V
OUT
Accuracy Over Line and Load
o
5-Bit On-Board DAC with Input Mux
o
Precision-Adjustable V
OUT
Slew Control
o
0.925V to 2V Output Adjust Range
o
Supports Voltage-Positioned Applications
o
2V to 28V Battery Input Range
o
Requires a Separate +5V Bias Supply
o
200/300/550/1000kHz Switching Frequency
o
Over/Undervoltage Protection
o
Drives Large Synchronous-Rectifier FETs
o
700µA typ I
CC
Supply Current
o
2µA typ Shutdown Supply Current
o
2V ±1% Reference Output
o
VGATE Transition-Complete Indicator
o
Small 24-Pin QSOP Package
MAX1717
The MAX1717 step-down controller is intended for core
CPU DC-DC converters in notebook computers. It fea-
tures a dynamically adjustable output, ultra-fast tran-
sient response, high DC accuracy, and high efficiency
needed 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 switching frequency.
The output voltage can be dynamically adjusted
through the 5-bit digital-to-analog converter (DAC)
inputs over a 0.925V to 2V range. A unique feature of
the MAX1717 is an internal multiplexer (mux) that
accepts two 5-bit DAC settings with only five digital
input pins. Output voltage transitions are accomplished
with a proprietary precision slew-rate control
†
that mini-
mizes surge currents to and from the battery while
guaranteeing “just-in-time” arrival at the new DAC setting.
High DC precision is enhanced by a two-wire remote-
sensing scheme that compensates for voltage drops in
the ground bus and output voltage rail. Alternatively,
the remote-sensing inputs can be used together with
the MAX1717’s high DC accuracy to implement a volt-
age-positioned circuit that modifies the load-transient
response to reduce output capacitor requirements and
full-load power dissipation.
Single-stage buck conversion allows these devices to
directly step down high-voltage batteries for the highest
possible efficiency. Alternatively, two-stage conversion
(stepping down the +5V system supply instead of the
battery) at a higher switching frequency allows the mini-
mum possible physical size.
The MAX1717 is available in a 24-pin QSOP package.
Ordering Information
PART
MAX1717EEG
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
24 QSOP
Minimal Operating Circuit
+5V INPUT
V
CC
MAX1717
V
DD
V+
BST
DH
BATTERY
2.5V TO 28V
Applications
Notebook Computers with SpeedStep™ or Other
Dynamically Adjustable Processors
2-Cell to 4-Cell Li+ Battery to CPU Core Supply
Converters
5V to CPU Core Supply Converters
Pin Configuration appears at end of data sheet.
†
Patent pending.
SKP/SDN
FBS
ILIM
GNDS
A/B
REF
TON
CC
D0
DAC
INPUTS
D1
D2
D3
D4
OUTPUT
0.925V TO 2V
LX
DL
GND
FB
TIME
VGATE
Quick-PWM is a trademark of Maxim Integrated Products.
SpeedStep is a trademark of Intel Corp.
________________________________________________________________
Maxim Integrated Products
1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
