Diodes AP9060 - Manual (Page 5)

AP9060
Document number: DS36001 Rev. 2 - 2
5 of 9
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August 2012
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T
AP9060
Application Information
Over-Voltage Protection
AP9060 protects sensitive circuits by clamping the input voltage to a safe level. In other words, AP9060 conditions the input voltage before
presenting it to the sensitive circuitry.
The clamp voltage on AP9060 is set to 11.15V (typically at room temperature). Therefore, the sensitive circuitry will not be exposed to a voltage
greater than 11.15V. As a consequence, it is important to ensure that the sensitive ICs that follow AP9060 are safe to operate up to the clamp
voltage level (refer to Figure 4 for variation in clamp voltage over temperature).
If the input voltage is below V
CLAMP
, the PMOS pass transistor in the AP9060 fully turns on and only I x R
ON
is dropped across the FET (where, I
is the current drawn by the sensitive ICs). On the other hand, if V
IN
is greater than the clamp voltage, then AP9060 limits the drive to the FET to
ensure that the voltage on VOUT is maintained at the clamp level.
Over-Temperature Protection
As a secondary protection mechanism, AP9060 incorporates an over-temperature shutdown feature. Therefore, if the sensitive circuitry draws
too much current either in normal mode or in the clamp mode, AP9060 will turn off the PMOS transistor, provided the junction temperature
exceeds the thermal shutdown threshold (THM
SD
). Thereafter, the device will resume normal operation once the junction temperature falls below
THM
SD
– THM
hyst
.
In the clamp mode, given that any input voltage above V
CLAMP
is dropped across the pass transistor in AP9060, care must be taken to keep the
power dissipation within AP9060 in check by minimising the current drawn in this mode.
Fast Input Transient Protection
AP9060 will also protect the sensitive circuits against fast input transients. Upon detecting a fast transient on VIN, AP9060 reduces the drive to
the FET in order to minimise the overshoot on VOUT. With 100nF on VOUT, if the voltage on VIN goes from 0V to 30V in 100ns, the output
voltage will not peak above V pk .
Reverse Operation
AP9060 supports the USB OTG specification and can operate in the reverse direction as well. Therefore, if the sensitive circuitry drives a voltage
on VOUT (V
OUT_REV
) and a load is connected on VIN (I
IN_REV
), then AP9060 will turn the FET on in the reverse direction and only I x R
ON
will be
dropped across the device, similar to the forward operation.
However, note that neither over-voltage nor over-temperature protection mechanisms will function in this mode.
Output Capacitor
It is recommended to have a capacitor on VOUT in a range between 100nF and 10µF.
Output Resistor
It is recommended to have a resistor on VOUT in a range between 10k Ω and 100kΩ.