Download MAX8857A Smallest, All-Internal MOSFET, 7-Channel 2 AA DSC PMIC General Description

ABRIDGED
19-0987; Rev 1; 2/12
KIT
ATION
EVALU
E
L
B
AVAILA
Smallest, All-Internal MOSFET,
7-Channel 2 AA DSC PMIC
The MAX8857A PMIC provides a complete power-supply solution for digital still cameras (DSCs) and digital
video cameras (DVCs). The MAX8857A improves performance, component count, and board space utilization 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 additional external components.
• Step-up synchronous-rectified DC-DC converter
(SU). The MAX8857A is bootstrapped from VSU.
•
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 converter (Z) for DSP DDR supply voltage.
•
Low-voltage (down to 1V) synchronous-rectified
step-down DC-DC converter (SD) for DSP core supply 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.
The MAX8857A has an independent/simultaneous
power-on sequence of the CCDBST and CCDINV converters. 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
TEMP
RANGE
PIN-PACKAGE
MAX8857AETL+
-40°C to
+85°C
40 Thin QFN-EP*
5mm x 5mm x 0.8mm
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
o
Internal Compensation on All Channels
True Shutdown™ on All Step-Up Converters
Overload Protection
Startup into Short Protection
Soft-Start for Controlled Startup Current
o 100% Duty Cycle on Step-Down Converters
o
o
o
o
Regulated Current Output for Up to 6 White LEDs
PWM Dimming of WLED Current
Adjustable LED Overvoltage Protection Up to 27V
Transformerless Inverting Converter for CCD
o 2MHz ±2.5% Switching Frequency
o 1µA Shutdown Supply Current
o CCD Voltage Sequencing
o All Internal Power MOSFETs
o SDOK Power-OK Indicator
Typical Operating Circuit
INPUT
1.8V TO 5.5V
PVBST
ONSU
PKG
CODE
T4055-2
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.
SU STEP-UP
MAIN STEP-UP
ONM
SD STEP-DOWN
ONSD
SDZ STEP-DOWN
ONZ
Ordering Information
PART
Features
VSU 5V
VMAIN 3.3V
VSD 1.8V
VDDRZ 2.5V
MAX8857A
SDOK
ONLED
LEDBST
VLEDBST UP TO 6 WLEDs
ONBST
CCDBST
VCCDBST +15V
ONINV
CCDINV
VCCDINV -7.5V
Pin Configuration appears at the end of data sheet.
True Shutdown is a trademark of Maxim Integrated Products, Inc.
________________________________________________________________ Maxim Integrated Products
1
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.
MAX8857A
General Description
ABRIDGED
MAX8857A
Smallest, All-Internal MOSFET,
7-Channel 2 AA DSC PMIC
VREF
C20
0.1µF
24
REF
VBATT
(1.8V TO 5.5V)
C1
22µF
C2
22µF
FBINV
PVSU
30 PVSU
C3
22µF
C4
22µF
R17
100Ω
R1
402kΩ
C21
0.1µF
SWBST
SU
R14
100kΩ
L6
2.2µH
LXBST
FBSU
FBBST
VBATT
L2
1µH
VMAIN
(3.3V, 300mA)
PVBST
C7
22µF
VBATT
C8
10µF
34
L3
4.7µH
VSD
(1.8V, 250mA)
C10
10µF
PVLED
SWLED
3
R4
10kΩ
FBM
PGM
(EP)
PVSD
7
R6
100kΩ
VBATT
28
VSU
4
NOTE 2:
ALL CONVERTERS’ POWER GROUND
CONNECTIONS ARE THROUGH THE
EXPOSED PADDLE (EP).
LXLED
OVLED
PVGD
FBLED
35
LXSD
C9
10µF
NOTE 1:
ALL ON_ PINS HAVE INTERNAL 1MΩ
PULLDOWN TO GROUND.
VCCDBST
(15V, 30mA)
C17
2.2µF
33
12
21
8
38
FBSD
PGSD
(EP)
VBATT
C16
1µF
VBATT
C14
1µF
18
13
14
L5
4.7µH
GND
PVZ
LXZ
C15
3.3µF
11
ONZ
R9
1.6MΩ
FBZ
PGZ
(EP)
SDOK
D6
VSU
C23
1µF, OPTIONAL
D5
R10
100kΩ
19
D4
9
R15
10Ω
25
VSU
C11
1µF
36
37
L4
4.7µH
VDDRZ
(2.5V, 200mA)
C13
10µF
R7
150kΩ
5
6
R8
100kΩ
R16
100kΩ
VBATT
Figure 1. MAX8857A Typical Application Circuit
14
D7
10
C12
10µF
ONLED
ONINV
VLEDBST
(16V, 25mA)
D1
ONSD
ONBST
R12
100kΩ
PGLED
(EP)
EP
ONSU
ONM
R11
1.4MΩ
22
LXM
1, 2 PVM
C6
22µF
VREF
D2
20
PGSU
(EP)
39,
40
R13
604kΩ
23
PGBST
(EP)
27
C5
1µF
C19
10µF
17
MAX8857A
26
R2
100kΩ
VCCDINV
(-7.5V, 100mA)
D3
LXSU
LXSU
29
VSU
(5V, 500mA)
C18
1µF
L7
10µH
31
R5
80.6kΩ
16
PVINV
15
LXINV
L1
2µH
32
R3
23.2kΩ
VBATT
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