BD6520F View Datasheet(PDF) - ROHM Semiconductor
Part Name
Description
Manufacturer
BD6520F Datasheet PDF : 17 Pages
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BD6520F,BD6522F
Technical Note
●Functional description
1. Switch operation
VDD pin and OUT pin are connected to the drain and the source of switch MOSFET respectively. And the VDD is used
also as power source input to internal control circuit.
When CTRL input is set to High level and the switch is turned on, VDD and OUT is connected by a 50mΩ switch. In a
normal condition, current flows from VDD to OUT. If voltage of OUT is higher than VDD, current flows from OUT to VDD,
since the switch is bidirectional.
In BD6520F, there is a parasitic diode between the drain and the source of switch MOSFET. Therefore, even when the
switch is off, if the voltage of OUT is higher than that of VDD, current flows from OUT to VDD. In BD6522F, there is not this
parasitic diode, it is possible to prevent current from flowing reversely from OUT to VDD.
2. Thermal shutdown
Thermal shut down circuit turns off the switch when the junction temperature exceeds 135℃(Typ.).
The switch off status of the thermal shut down is latched. Therefore, even when the junction temperature goes down,
switch off is maintained. To release the latch, it is necessary to input a signal to switch off to CTRL terminal or make UVLO
status. When the switch on signal is input or UVLO is released, the switch output is recovered.
The thermal shut down circuit works when CTRL signal is active.
3. Low voltage malfunction prevention circuit (UVLO)
The UVLO circuit monitors the voltage of the VDD pin, when the CTRL input is active. UVLO circuit prevents the switch
from turning on until the VDD exceeds 2.5V(Typ.). If the VDD drops below 2.3V(Typ.) while the switch turns on, then UVLO
shuts off the switch.
4. Soft start control
In BD6520F/BD6522F, soft start is carried out in order to reduce inrush current at switch on. Further, in order to reduce
inrush current, soft start control pin (SSCTL) is prepared.
By connecting external capacitor to between SSCTL and GND, it is possible to make smoother the switch rise time. When
the switch is enabled, SSCTL outputs voltage of about 13.5V.
SSCTL terminal requires high impedance, so pay attention in packaging it so that there should not be leak current. And
when voltage is impressed from the outside to SSCTL terminal, switch on, off cannot be made correctly.
5. Discharge circuit
When the switch between the VDD and the OUT is OFF, the 200Ω(Typ.) discharge switch between OUT and GND turns on.
By turning on this switch, electric charge at capacitive load is discharged.
In BD6522F, the input of discharge circuit is separately prepared as DISC pin. When to use the discharge circuit, connect
OUT pin and DISC pin outside.
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12/16
2011.05 - Rev.B
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