Rainbow Electronics MAX17031 - Manual

General Description
The MAX17031 is a dual Quick-PWM™ step-down
power-supply (SMPS) controller with synchronous recti-
fication, intended for main 5V/3.3V power generation in
battery-powered systems. Low-side MOSFET sensing
provides a simple low-cost, highly efficient current
sense for valley current-limit protection. Combined with
the output overvoltage and undervoltage protection fea-
tures, this current limit ensures robust output supplies.
The 5V/3.3V SMPS outputs can save power by operat-
ing in pulse-skipping mode or in ultrasonic mode to
avoid audible noise. Ultrasonic mode forces the con-
troller to maintain switching frequencies greater than
20kHz at light loads. The SKIP input also has an accu-
rate logic threshold, allowing it to be used as a sec-
ondary feedback input to refresh an external charge
pump or secondary winding without overcharging the
output voltages.
An internal 100mA linear regulator generates the 5V
bias needed for power-up or other low-power “always-
on” suspend supplies. An internal bypass circuitry
allows automatic bypassing of the linear regulator when
the 5V SMPS is active.
The device includes independent shutdown controls
with well-defined logic thresholds to simplify power-up
and power-down sequencing. To prevent current
surges at startup, the internal voltage target is slowly
ramped up from zero to the final target over a 1ms peri-
od. To prevent the output from ringing below ground in
shutdown, the internal voltage target is ramped down
from its previous value to zero over a 1ms period. A
combined power-good (PGOOD) output simplifies the
interface with external controllers. The MAX17031 is
available in a 24-pin thin QFN (4mm x 4mm) package.
Applications
Notebook Computers
Ultra-Mobile PC
Main System Supply (5V and 3.3V Supplies)
2 to 4 Li+ Cells Battery-Powered Devices
Telecommunication
Features
♦ Dual Quick-PWM
♦ Preset 5V and 3.3V Outputs
♦ Internal 100mA, 5V Linear Regulator
♦ Internal OUT1 LDO5 Bypass Switch
♦ Secondary Feedback (SKIP Input) Maintains
Charge Pump
♦ 3.3V, 5mA Real-Time Clock (RTC) Power (Always
On)
♦ 2V ±1% 50µA Reference
♦ 6V to 24V Input Range
♦ Pulse-Skipping/Forced-PWM/Ultrasonic Mode
Control
♦ Independent SMPS and LDO5 Enable Controls
♦ Combined SMPS PGOOD Outputs
♦ Minimal Component Count
MAX17031
Dual Quick-PWM Step-Down Controller with Low-
Power LDO and RTC Regulator for MAIN Supplies
________________________________________________________________ Maxim Integrated Products 1
23
*EXPOSED PAD.
*EP
24
22
21
8
7
9
ONLDO
RTC
IN
LDO5
10
REF
DL2 V
DD
DL1 BST2 BST1
1 2
SKIP
4 5 6
17 18 16 14 13
OUT2
ILIM2
ON1
PGOOD
ILIM1
OUT1
MAX17031
V
CC
GND
3
15
ON2
20 11 DH1 DH2
19 12 LX1 LX2
THIN QFN
4mm × 4mm
TOP VIEW
+
Pin Configuration
Ordering Information
19-4305; Rev 0; 10/08
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
+ Denotes a lead-free/RoHS-compliant package.
* EP = Exposed pad.
PART TEMP RANGE PIN-PACKAGE
MAX17031ETG+ -40
°C to +85°C
24 TQFN-EP*
Quick-PWM is a trademark of Maxim Integrated Products, Inc.