AT1305
Preliminary Product Information
PFM Step-Up DC/DC Converter with LDO
Function Description
Boost Converter
The AT1305 integrates a step-up, switch-mode DC/DC converter with a linear
regulator to provide step up/down voltage conversion. A pulse frequency modulation
(PFM) with a constant on time 4.5us and minimum off-time 1.4µs controls the
N-channel MOSFET. The linear regulator contains a P-channel MOSFET. In 1-cell or
2-cell battery input (When VBAT <VOUT), only the step-up regulator is active, and
the linear regulator behaves as a pass gate. The output voltage can be adjusted with
two external resistors. The formula show as follow equation.
R1
R2
VDD = V 1+
FB
R1
= 1.2× (1+
)
The maximum efficiency could be 89% over 50mA load range. The AT1305
guarantee starts up as low as 1.0V input.
LDO mode
The low-dropout linear regulator consists of a reference, an error amplifier and a
P-channel MOSFET. In USB mode, when VIN>4V, the linear regulator is active
automatically whether the EN and /ENPB is enabled or not. The output voltage is
default 3.3V, 3.0V and 1.8V version. Its driving capability is nearly 250mA.
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
2/8/2006 REV:1.1
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
10
AIMTRON [ AIMTRON TECHNOLOGY ]
