Rainbow Electronics MAX1791 - Manual

General Description
The MAX1762/MAX1791 PWM step-down controllers
provide high efficiency, excellent transient response,
and high DC output accuracy needed for stepping
down high-voltage batteries to generate low-voltage
CPU core, I/O, and chipset RAM supplies in notebook
computers and PDAs.
Maxim’s proprietary Quick-PWM™ pulse-width modula-
tor is a free-running constant on-time type with input
feed-forward. Its high operating frequency (300kHz)
allows small external components to be utilized in PC
board area-critical applications such as subnotebook
computers and smart phones. PWM operation occurs
at heavy loads, and automatic switchover to pulse-skip-
ping operation occurs at lighter loads. The external
high-side P-channel and low-side N-channel MOSFETs
require no bootstrap components. The MAX1762/
MAX1791 are simple, easy to compensate, and do not
have the noise sensitivity of conventional fixed-frequen-
cy current-mode PWMs.
These devices achieve high efficiency at a reduced
cost by eliminating the current-sense resistor found in
traditional current-mode PWMs. Efficiency is further
enhanced by their ability to drive synchronous-rectifier
MOSFETs. The MAX1762/MAX1791 come in a 10-pin
µMAX package and offer two fixed voltages (Dual
Mode™) for each device, 1.8V/2.5V/adj (MAX1762) and
3.3V/5.0V/adj (MAX1791).
________________________Applications
Notebooks Handy-Terminals
Subnotebooks PDAs
Digital Cameras Smart Phones
1.8V/2.5V Logic
and I/O Supplies
Features
♦ High Operating Frequency (300kHz)
♦ No Current-Sense Resistor
♦ Accurate Current Limit
♦ ±1% Total DC Error over Line and During
Continuous Conduction
♦ Dual Mode Fixed Output
1.8V/2.5V/adj (MAX1762)
3.3V/5.0V/adj (MAX1791)
♦ 0.5V to 5.5V Output Adjust Range
♦ 5V to 20V Input Range
♦ Automatic Light-Load Pulse Skipping Operation
♦ Free-Running On-Demand PWM
♦ Foldback Mode™ UVLO
♦ PFET/NFET Synchronous Buck
♦ 4.65V at 25mA Linear Regulator Output
♦ 5µA Shutdown Supply Current
♦ 230µA Quiescent Supply Current
♦ 10-Pin µMAX Package
MAX1762/MAX1791
High-Efficiency, 10-Pin µMAX, Step-Down
Controllers for Notebooks
________________________________________________________________ Maxim Integrated Products 1
19-1923; Rev 0; 1/01
Ordering Information
PART TEMP. RANGE PIN-PACKAGE
MAX1762EUB -40 °C to +85°C 10 µMAX
MAX1791EUB -40 °C to +85°C 10 µMAX
FB
GND
CS
DH
VP
DL OUT
REF
SHDN
V BATT
(5V TO 20V)
V OUT
1.8V/3.3V
VL
MAX1762
MAX1791
Typical Operating Circuit
1
2
3
4
5
10
9
8
7
6
DH
CS
DL OUT
FB
REF
VL
MAX1762
MAX1791
µMAX
TOP VIEW
GND SHDN
VP
Pin Configuration
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.
Quick-PWM, Dual Mode, and Foldback Mode are a trade-
marks of Maxim Integrated Products.