Rainbow Electronics MAX1717 - Manual

General Description
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.
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
Features
♦ Quick-PWM Architecture
♦ ±1% V
OUT Accuracy Over Line and Load
♦ 5-Bit On-Board DAC with Input Mux
♦ Precision-Adjustable V
OUT Slew Control
♦ 0.925V to 2V Output Adjust Range
♦ Supports Voltage-Positioned Applications
♦ 2V to 28V Battery Input Range
♦ Requires a Separate +5V Bias Supply
♦ 200/300/550/1000kHz Switching Frequency
♦ Over/Undervoltage Protection
♦ Drives Large Synchronous-Rectifier FETs
♦ 700µA (typ) I
CC Supply Current
♦ 2µA (typ) Shutdown Supply Current
♦ 2V ±1% Reference Output
♦ VGATE Transition-Complete Indicator
♦ Small 24-Pin QSOP Package
MAX1717
Dynamically Adjustable, Synchronous
Step-Down Controller for Notebook CPUs
________________________________________________________________ Maxim Integrated Products 1
19-1636; Rev 2; 2/02
PART
MAX1717EEG -40°C to +85°C
TEMP RANGE PIN-PACKAGE
24 QSOP
Ordering Information
Pin Configuration appears at end of data sheet.
† Patent pending.
Quick-PWM is a trademark of Maxim Integrated Products.
SpeedStep is a trademark of Intel Corp.
TIME
VGATE
DH
LX
DL
BST
+5V INPUT
ILIM
GNDS
FBS
D0
D1
D2
D3
D4
REF
TON
GND
FB
MAX1717
CC
V+
V CC V DD
SKP/SDN
OUTPUT
0.925V TO 2V
DAC
INPUTS
BATTERY
2.5V TO 28V
A/B
Minimal Operating Circuit
EVALUATION KIT
AVAILABLE
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.