S-8338ABDC-P8T1G

The S-8338ABDC-P8T1G is a member of the DC DC Switching Controllers Power Management IC (PMIC) voltage regulator series manufactured by Sanken. By establishing a power conversion system using a controller, buck converter, etc., the power supply design is simplified to reduce the circuit size. It has a built-in micro-step control, high-efficiency PWM control, and current limit, and is capable of wide-range output current control.

Applications

• Power supplies that require high-efficiency products, such as information equipment and digital AV equipment
• Battery-powered equipment where size and weight are constraints
• General AC/DC, DC/DC conversion applications
• Stationary power supplies

Working Principle

Using a buck converter topology, the S-8338ABDC-P8T1G implements current limit and PWM control using an analog IC. When an input voltage is applied, current is first switched on to a constant current source at each level resistor connected to a ground terminal through the peak current detect input of the output feedback comparator. The output of the output comparator is connected to the current limit circuit, and the voltage detected by the peak current detect is used to set the parameter of the current limit circuit for the peak current limit.

The voltage impressed on the output of the peak current detect circuit is made to follow the voltage impressed on the input side of the control block by applying a control signal from the pulse width modulation control block. The output voltage limit is monitored by an output feedback comparator having an input signal from the output feedback divider. The output voltage is adjusted by measuring the voltage of the adjusting pin with an internal voltage reference, which is then compared to the voltage impressed on the output of the output feedback divider.

The output signal of the output feedback comparator is used to control the pulse width modulator, and the output of the modulator is connected to the gate driver, which in turn is connected to the low side MOSFET of the power switching circuit. The inductor current is ramped up and down using the pulse width modulation control signal and then is switched off by the low side MOSFET. The output of the modulator is also connected to the internal current limit circuit to monitor the output load current. The load current is monitored and the current limit value is adjusted according to the voltage detected by the peak current monitor circuit.

In order to maintain the output voltage, the stabilizing circuit is also connected to the output feedback comparator and the voltage reference through the pulse width modulation control block. A voltage drop is applied across the voltage divider connected to the output to give a feedback signal to the output feedback comparator. The output voltage is then regulated to the voltage level corresponding to the voltage impressed on the input of the output feedback comparator. The SMPS contains both the current limit circuit and the stabilizing circuit to meet the needs of many output current and voltage applications.