MAX8720 Datasheet, PDF (1/31 Pages) Maxim Integrated Products – Dynamically Adjustable 6-Bit VID Step-Down Controller

19-3319; Rev 1; 8/04
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Dynamically Adjustable 6-Bit VID
Step-Down Controller
General Description
The MAX8720 step-down controller is intended for core
CPU DC-DC converters in notebook computers. It fea-
tures a dynamically adjustable output, ultra-fast transient
response, high DC accuracy, and the 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 6-bit digital-to-analog converter (DAC) over a 0.275V
to 1.850V range in 25mV steps. The MAX8720 has inde-
pendent four-level logic inputs for setting the suspend
voltage (S0-S1). Precision slew-rate control provides
“just-in-time” arrival at the new DAC setting, minimizing
surge currents to and from the battery. The internal DAC
of the MAX8720 is synchronized to the slew-rate clock
for improved operation under aggressive power man-
agement of newer chipsets and operating systems that
can make incomplete mode transitions. Remote feed-
back and ground-sense inputs allow easy compensa-
tion for IR drops in PC board traces.
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 MAX8720 is available in a 28-pin QSOP or 36-pin
6mm x 6mm thin QFN package.
Applications
CPU Core Supply Converters
GPU Core Supply Converters
Notebook and Subnotebook Computers
Quick-PWM is a trademark of Maxim Integrated Products, Inc.
Pin Configurations appear at end of data sheet.
Features
♦ Quick-PWM Architecture
♦ ±1% V_OUT Accuracy Over Line and Load
♦ 6-Bit On-Board DAC with Input Muxes
♦ Precision-Adjustable V_OUT Slew Control
♦ 0.275V to 1.850V Output Adjust Range
♦ Remote Feedback and Ground Sense
♦ Supports Voltage-Positioned Applications
♦ 2V to 28V Battery Input Range
♦ 200kHz/300kHz/550kHz/1000kHz Switching
Frequency
♦ Over/Undervoltage Protection
♦ Drives Large Synchronous-Rectifier FETs
♦ 800µA (typ) I_CC Supply Current
♦ 10µA (typ) Shutdown Supply Current
♦ 2V ±0.75% Reference Output
♦ PGOOD Blanking During Transition
Ordering Information
PART
MAX8720EEI
MAX8720ETX
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 QSOP
36 Thin QFN 6mm x 6mm
Minimal Operating Circuit
+5V BIAS
V_CC
V_DD
SHDN
V+
ILIM
BST
AGND
DH
SKIP
SUS
LX
MAX8720 DL
PGOOD
VID0
D0
PGND
VID1
D1
VID2
D2
VID3
D3
VID4
D4
VID5
D5
S0
S1
FB
FBS
GNDS
CC
REF
TIME
INPUT (V_IN)
7V TO 28V
OUTPUT (V_OUT)
0.275V TO 1.850V
________________________________________________________________ Maxim Integrated Products 1
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.