AT1454/AT1454A/AT1454B
Preliminary Product Information
Photoflash Capacitor Charger for DSC
Adjustable Input Current
The AT1454/1454A/B can adjust N-MOS switch on-time by a resistor connecting to
Rsense pin. This resistor determines the primary peak current and on-time of primary
N-MOS as the following equation:
−6
VBAT × 2×10
V
25KΩ
R4 + 25KΩ
IPK −PRI
=
,VRsense =VBAT (or,VCC ) ×
Rsense × LPRI
IPK −PRI × LPRI
TON
=
VBAT
where
LPRI: primary inductance (µH)
IPK-PRI: peak primary current (A)
R4: It is recommended several KΩ grade
If setting constant on-time by a resistor R10 is connected to VCC, then R4 resistor
need to remove from application circuitry. In this case, on-time is a constant. At
another topology, if R4 connect to VBAT to set constant on-time, then R10 need to
remove from application circuitry. However, on-time can change dependent on VBAT
because battery voltage level is different from full energy to low power. External
capacitor Css is connected to VCC and Rsense to perform soft-start function to reduce
inrush current on VBAT input current and avoid the internal switching noise.
T1
ST-982610A
1:25
L1 33uH
/Option
VBAT
R10
10uH/6.1mH
C1
22u/6V3
VCC
R4
Css
0.1uF
VCC
Rsense
LX
Isec
AT1454/AT1454A/AT1454B
7F, No.9,PARK AVENUE. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
3/24/2006 REV:1.2
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
15
AIMTRON [ AIMTRON TECHNOLOGY ]
