A7545
DC-DC CONVERTER/BOOST (STEP-UP)
AiT Semiconductor Inc.
www.ait-ic.com
LOW-NOISE 4.5A STEP-UP CURRENT MODE PWM CONVERTER
DETAILED INFORMATION
Operation
The A7545 is a current mode boost converter. The switching frequency is 1MHz and operates with pulse
width modulation (PWM). Build-in 12V / 4.5A MOSFET provides a high output voltage. The control loop
architecture is peak current mode control; therefore slope compensation circuit is added to the current signal
to allow stable operation for duty cycles larger than 50%.
Soft Start Function
Soft start circuitry is integrated into A7545 to avoid inrush current during power on. After the IC is enabled, the
output of error amplifier is clamped by the internal soft-start function, which causes PWM pulse width
increasing slowly and thus reducing input surge current.
Current Limit Program
A resistor between OC and GND pin programs peak switch current. The resistor value should be between 26k
to 500k. The current limit will be set from 4.5A to 0.5A. Keep traces at this pin as short as possible. Do not put
capacitance at this pin. To set the over current trip point according to the following equation:
Over Temperature Protection (OTP)
A7545 will turn off the power MOSFET automatically when the internal junction temperature is over 150°C.
The power MOSFET wake up when the junction temperature drops 30°C under the OTP threshold
temperature.
Over Voltage Protection (OVP)
In some condition, the resistive divider may be unconnected, which will cause PWM signal to operate with
maximum duty cycle and output voltage is boosted higher and higher. The power MOSFET will be turned off
immediately, when the output voltage exceeds the OVP threshold level. The A7545’s OVP threshold is 12V.
REV1.0
- JUN 2014 RELEASED -
- 5 -
AITSEMI [ AiT Semiconductor ]
