bd9324efj ROHM Co. Ltd., bd9324efj Datasheet - Page 4

• Manufacturer Part Number: bd9324efj
• Description: Simple Step-down Switching Regulator With Integrated Compensation
• Manufacturer: ROHM Co. Ltd.

•VREG
•VREF
•TSD/UVLO
•Error amp block (ERR)
•Oscillator block (OSC)
•SLOPE block
•PWM block
•DRV block
• CURRENT SENSE
• DELAY START
•Soft start circuit
Block Operation
A block to generate constant-voltage for DC/DC boosting.
A block that generates internal reference voltage of 2.9 V (Typ.).
TSD (Thermal shutdown)/UVLO (Under Voltage Lockout) protection block. The TSD circuit shuts down IC at 175℃ (Typ.)
The UVLO circuit shuts down the IC when the Vcc is Low Voltage.
This is the circuit to compare the reference voltage and the feedback voltage of output voltage. The COMP pin voltage resulting
from this comparison determines the switching duty. At the time of startup, since the soft start is operated by the SS pin voltage,
the COMP pin voltage is limited to the SS pin voltage.
This block generates the oscillating frequency.
This block generates the triangular waveform from the clock created by OSC. Generated triangular waveform is sent to the PWM
comparator.
The COMP pin voltage output by the error amp is compared to the SLOPE block's triangular waveform to determine the
switching duty. Since the switching duty is limited by the maximum duty ratio which is determined internally, it does not become
100%.
A DC/DC driver block. A signal from the PWM is input to drive the power FETs.
Current flowing to the power FET is detected by voltage at the CURRENT SENSE and the overcurrent protection operates at
2.5/3.5/4.5A (min.). When the overcurrent protection operates, switching is turned OFF and the SS pin capacitance is
discharged.
A start delay circuit for positive/negative charge pump and Boost converter.
Since the output voltage rises gradually while restricting the current at the time of startup, it is possible to prevent the output
voltage overshoot or the rush current.
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