AT5802
Preliminary
4-Channel driver + Power Controller
4.Soft start
The soft-start is functioned by putting a capacitor between SOFT terminal and GND.
5. Short circuit protection
If the voltage of SPRT terminal has reached 0.5V, switching of SW terminal is disabled. The main
DC/DC converter can be turned off only through the activation of timer latch circuit. Accordingly be
sure to attach the capacitor on the SPRT terminal.
While the error amp output of EO is being completely set at “H”, SPRT terminal can be charged.
The time until stopping the switching is determined by the following formula for the capacitor
of SPRT terminal.
VTH
ISPRT
t = CSPRT
×
(sec) (VTH=0.5V, ISPRT=5.8 A)
While the OFF terminal is being set at below VSYS-1.5V, SPRT terminal can be charged. The
time until stopping the switching is determined by the following formula for the capacitor of
SPRT terminal.
VTH
ISPRT
t = CSPRT
×
(sec) (VTH=0.5V, ISPRT=11.5 A)
6. PWM driver
H-bridge driver using 4 pieces of N-channel Mos transistor on output stage. Polarity of output and
PWM duty are changed in proportion to differential voltage and absolute value of input sandwiching
Vref. Load is direct-PWM driven by square wave of this changing duty. This driver is voltage
feedback type, so, voltage gain is invariable in spite of fluctuation of battery voltage.
7. Thermal shut down
When the chip temperature has been 150
(Typ.), the output current is muted. And when the
chip temperature has dropped to 130 (Typ.), the driver circuit starts up.
2F, No.10, Prosperity RD. II, Science-Based Industrial Park, Hsinchu 300,Taiwan, R.O.C.
Tel: 886-3-563-0878
Fax: 886-3-563-0879
WWW: http://www.aimtron.com.tw
Email: service@aimtron.com.tw
10
GMT [ GLOBAL MIXED-MODE TECHNOLOGY INC ]
