19-0987; Rev 1; 2/12
ABRIDGED
Smallest, All-Internal MOSFET,
7-Channel 2 AA DSC PMIC
General Description
Features
o
95% Efficient Synchronous-Rectified DC-DC
Converters
o
90% Efficient Boost-Buck Operation
o
Up to 85% Efficient, High-Voltage DC-DC
Converters
o
Inverter Operates Directly from 2 AA Batteries
o
o
o
o
Internal Compensation on All Channels
True Shutdown™ on All Step-Up Converters
Overload Protection
Startup into Short Protection
IT
TION K
VALUA
E
BLE
AVAILA
MAX8857A
The MAX8857A PMIC provides a complete power-sup-
ply solution for digital still cameras (DSCs) and digital
video cameras (DVCs). The MAX8857A improves per-
formance, component count, and board space utiliza-
tion compared to currently available solutions for 2 AA
cell and dual-battery designs. On-chip power
MOSFETs provide up to 95% efficiency for critical
power supplies. The CCD inverter can operate directly
from 2 AA/NiMH batteries without the use of any addi-
tional external components.
• Step-up synchronous-rectified DC-DC converter
(SU). The MAX8857A is bootstrapped from V
SU
.
•
•
•
MAIN synchronous-rectified step-up DC-DC converter
(M) with active discharge for DSP I/O supply voltage.
SDZ synchronous-rectified step-down DC-DC con-
verter (Z) for DSP DDR supply voltage.
Low-voltage (down to 1V) synchronous-rectified
step-down DC-DC converter (SD) for DSP core sup-
ply voltage.
Step-up DC-DC converter with current regulation
and PWM dimming control (LEDBST) for up to 6
series white LEDs (WLED).
High-voltage step-up DC-DC converter (CCDBST)
for CCD imagers or positive LCD bias supplies.
Transformerless inverting DC-DC converter (CCDINV)
for CCD imagers or negative LCD bias supplies.
This
converter can connect directly to 2 AA batteries.
o
Soft-Start for Controlled Startup Current
o
100% Duty Cycle on Step-Down Converters
o
Regulated Current Output for Up to 6 White LEDs
o
PWM Dimming of WLED Current
o
Adjustable LED Overvoltage Protection Up to 27V
o
o
o
o
o
o
Transformerless Inverting Converter for CCD
2MHz ±2.5% Switching Frequency
1µA Shutdown Supply Current
CCD Voltage Sequencing
All Internal Power MOSFETs
SDOK Power-OK Indicator
•
•
•
Typical Operating Circuit
INPUT
1.8V TO 5.5V
PVBST
ONSU
ONM
ONSD
ONZ
SDOK
ONLED
ONBST
ONINV
LEDBST
CCDBST
CCDINV
V
LEDBST
UP TO 6 WLEDs
V
CCDBST
+15V
V
CCDINV
-7.5V
SU STEP-UP
MAIN STEP-UP
SD STEP-DOWN
SDZ STEP-DOWN
V
SU
5V
V
MAIN
3.3V
V
SD
1.8V
V
DDRZ
2.5V
The MAX8857A has an independent/simultaneous
power-on sequence of the CCDBST and CCDINV con-
verters. For a preset power-on sequence of CCDBST
before CCDINV, contact the factory.
The MAX8857A is available in a 5mm x 5mm, 40-pin thin
QFN package and operates over the -40°C to +85°C
extended temperature range.
Applications
DSCs and DVCs
PDAs and Portable Media Players
Ordering Information
PART
MAX8857AETL+
TEMP
RANGE
-40°C to
+85°C
PIN-PACKAGE
40 Thin QFN-EP*
5mm x 5mm x 0.8mm
PKG
CODE
T4055-2
MAX8857A
MAX8857AETL+ -40°C to 40 Thin QFN-EP*
T4055-2
TCBR
+85°C
5mm x 5mm x 0.8mm
+Denotes
a lead-free package.
*EP
= Exposed paddle.
Note:
Contact factory for the option where CCDBST must
reach regulation before the INV converter can be turned on.
Pin Configuration appears at the end of data sheet.
True Shutdown is a trademark of Maxim Integrated Products, Inc.
1
________________________________________________________________
Maxim Integrated Products
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.
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