BD9E302EFJ Datasheet, PDF (4/44 Pages) Rohm – Integrated MOSFET Single Synchronous Buck DC/DC Converter

BD9E302EFJ
Datasheet
 Description of Blocks
 VREG3
Block creating internal reference voltage 3V (Typ).
 VREG
Block creating internal reference voltage 5V (Typ).
 BOOTREG
Block creating gate drive voltage.
 TSD
This is thermal shutdown block. Usually IC operating in the allowable power dissipation, but when the IC power dissipation
more than rating value, Tj will increase, when the chip temperature exceeds 175C (Typ), The thermal shutdown circuit is
intended for shutting down internal power devices. Then the Tj will decreased and IC restart. It is not meant to protect or
guarantee the soundness of the application. Do not use the function of this circuit for application protection design.
 UVLO
This is under voltage lockout block. Avoid the IC miss operation at low VIN or VIN start up, IC shuts down when VIN under
6.4V (Typ). When UVLO release, the IC restart, Still the threshold voltage has hysteresis of 200mV (Typ).
 ERR
The ERR block is an error amplifier and its inputs are the reference voltage 0.8 V (Typ) and the “FB” pin voltage. (Refer to
recommended examples on page 33). The output “COMP” pin controls the switching duty, the output voltage is set by
“FB” pin with external resistors. Moreover, the external resistor and capacitor are required to COMP pin as phase
compensation circuit.
 OSC
Block generating oscillation frequency.
 SLOPE
Creates delta wave from clock, generated by OSC, and sends voltage composed by current sense signal of high side
MOSFET and delta wave to PWM comparator.
 PWM
Settles switching duty by comparing output COMP terminal voltage of error amplifier and signal of SLOPE part.
 DRIVER LOGIC
This is DC/DC driver block. Input signal from PWM and drives MOSFET.
 SOFT START
By controlling current output voltage starts calmly preventing over shoot of output voltage and inrush current.
 OCP
Current flowing in high side MOSFET is controlled one circle each of switching frequency when over current occurs.
 SCP
The short circuit protection block compares the FB terminal voltage with the internal standard voltage VREF. When the FB
terminal voltage has fallen below 0.56 V (Typ) and remained there for 0.9 msec (Typ), SCP stops the operation for 14.4
msec (Typ) and subsequently initiates a restart.
 OVP
Over voltage protection function (OVP) compares FB terminal voltage with the internal standard voltage VREF. When the
FB terminal voltage exceeds 1.04V (Typ) it turns MOSFET of output part MOSFET OFF. After output voltage drop it
returns with hysteresis.
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