Low Voltage 2MHz Step-Up DC/DC
Converter in SC70JW Package
Functional Block Diagram
VCC
VIN
OUT
AAT1265
Start-Up
Inrush Control
V
REF
Low Voltage
Start-Up
Voltage
Reference
Mode
Control
DH
2MHz
Oscillator
Current
Sense
Logic
LX
Comp.
DL
Error
Amp.
GND
EN
GND
Functional Description
The AAT1265 synchronous step-up converter is
targeted for single- or dual-cell alkaline, NiMH, and
NiCd battery applications. It has a 1V typical start-
up voltage with operation after start-up to less than
0.8V.
The high 2MHz switching frequency of the
AAT1265 facilitates output filter component size
reduction for improved power density and reduced
overall footprint. It also provides greater bandwidth
and improved transient response over other lower
frequency step-up converters. The compensation
and feedback is integrated with only three external
components (C
IN
, C
OUT
, L).
Low R
DS(ON)
synchronous power switches provide
high efficiency for heavy load conditions. Switching
8
frequency modulation and low quiescent current
maintains this high efficiency for light load and
sleep mode conditions.
In addition to the improved efficiency, the synchro-
nous boost has the added performance advantage
of true load disconnect during shutdown (<1µA
shutdown current), inrush current limit, and short-
circuit protection.
PWM / PFM Control
The AAT1265 is a fixed frequency PWM peak cur-
rent mode control step-up converter. For light load
conditions (10 to 20mA and below), the converter
transitions to a variable frequency (PFM) mode to
reduce the dominant switching losses. In addition
to PFM operation, a zero current comparator
blocks reverse current in the P-channel synchro-
1265.2006.05.1.1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
