BD9E151NUX Datasheet, PDF (3/22 Pages) Rohm – 1ch Step-Down Switching Regulator

BD9E151NUX
Datasheet
Description of Blocks
1. Reference
This block generates reference voltage and current. It start operation by applying EN=H.
It provides reference voltage and current to error amplifier, oscillator, and etc.
2. REG
This is a gate drive voltage generator and 5.5V regulator for internal circuit power supply.
3. OSC
This is a precise wave oscillation circuit with operation frequency fixed to 600 kHz
4. Soft Start
This block does Soft Start to the output voltage of DC/DC converter, and prevents in-rush current during Start-up.
Soft Start Time set by the capacitor connected to SS pin and SS charge current is the time from EN Pin start-up
to reaching to 1.0V.
5. ERROR AMP
This is an error amplifier that detects output signal, and outputs PWM control signal. Internal reference voltage is set
to 1.0V. Connect phase compensation components between this pin and ground (ref. p.11).
6. OVP
The OVP circuit includes an overvoltage comparator to compare the FB pin voltage and internal thresholds. When the
FB pin voltage goes above 110%×FB, the high-side MOSFET will be forced off. When the FB pin voltage falls
below 105%, the high-side MOSFET will be enabled again.
7. ICOMP
The BD9E151NUX implements current mode control that uses the VC pin voltage to turn off the high-side MOSFET on a
cycle by cycle basis. Every cycle the switch current and the COMP pin voltage are compared; when the peak inductor
current intersects the VC pin voltage, the high-side switch is turned off. During overcurrent conditions that pull the output
voltage low, the error amplifier responds by driving the COMP pin high, causing the switch current to increase.
8. OCP
This is a circuit to protect the high-side FET from overcurrent. Every cycle the switch current and the reference voltage
of overcurrent protection are compared; when the peak inductor current intersects the reference voltage, the high-side
switch is turned off. Once overcurrent is detected, the device will stop and VC pin voltage will be reset and SS pin
voltage will be discharged by 2uA (hiccup operation). Then SS pin voltage reaches to less than 0.1V, IC will restart.
9. High-side MOSFET
This is a 30V/80mΩ high-side MOSFET that converts inductor current of DC/DC converter.
Because the current limiting of this FET is 1.6A included ripple current, please use at within1.6A.
10. UVLO
This is a low voltage error prevention circuit.
This prevents internal circuit error during increase of power supply voltage and during decline of power supply voltage.
It monitors VIN pin voltage and internal REG voltage, and when VIN voltage becomes 5.2V and below, it turns OFF all
output FET and turns OFF DC/DC comparator output and Soft Start circuit resets.
Now this Threshold has hysteresis of 200mV.
11. TSD
This is a heat protect circuit.
When it detects an abnormal temperature exceeding maximum junction temperature (Tj=150℃), it turns OFF all Output
FET, and turns OFF DC/DC converter output. When temperature falls, it automatically returns.
12. EN
When a Voltage of 2.4V or more is applied, it turns ON, at Open or 0V application, it turns OFF.
About 700kΩ Pull-down Resistance is contained within the Pin.
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TSZ22111・15・001
3/19
TSZ02210-0Q3Q0AZ00160-1-2
2013.07.17 Rev.001