HDP01-0512N Datasheet, PDF (4/6 Pages) STMicroelectronics – HARD DISK DRIVE POWER SUPPLY PROTECTION

HDP01-0512N
APPLICATION INFORMATION
DESCRIPTION
The HDP01-0512N has been specially designed to protect equipment supplied by both +5 and +12 Volt
power rails such as hard disk drives, CD-ROMs, DVDs, floppy disk drives with the topology indicated in
figure A.1.
Fig. A.1: typical application schematic.
+12V supply rail
+5V supply rail
ELECTRONIC
MODULE
(i.e. Disk drive)
This protection device is able to protect both +5 and
+12 Volts power rails against transients and rails in-
version.
The internal +5V protection is achieved with a crowbar
structure whereas the +12V one is secured by a
clamping structure.
ABOUT THE +5V PROTECTION
In normal conditions, (region – of figure A.2) the +5V protection (PL5 termination) of the HDP01-0512N
connected to the +5V rail, is in idle state and its leakage current is 1µA max at +5V @ 25°C. Upon occur-
rence of transients, the HDP01-0512N eliminates the overvoltage by clamping up to a maximum of +7.4V
(region — ) since the current induced by the transient does not exceed the activation current IA min (10mA).
If the IA min current value is passed, the internal +5V protection trips in crowbar mode (region ˜ ) and then
a short circuit appears on the +5V rail .
Fig. A.2: Current and voltage characteristic of the
+5V protection.
I
3
I_H
I_A
1
The arrows indicate the way the device is activated
from point — to point ˜ , and the way it goes back in
idle state, point ˜ to point –
Thanks to this behavior the electronic module (i.e.
disk drive) connected to the +5V rail is safe.
2
V
V_A
As soon as the transient disappears and assuming that the current in the +5V power supply rail is under the
holding current IHmin value (10mA) of the +5V protection, the HDP01-0512N gets back in idle state and the
protected electronic module turns back on. As in many cases the current delivered by the +5V power supply
is higher than the IH min current value of the HDP01-0512N, it is necessary to use a serial protection on the
+5V rail (i.e. resettable fuse), connected before the HDP protection. This will prevent the HDP01-0512N
from being damaged by an over-rated dissipated power. The choice of the serial protector is led by both
peak current and current duration the HDP01-0512N is able to support. The serial protection shall fulfill the
next condition :
i²t serial protection < ITSM @ tp of +5V HDP protection.
4/6