HV100K5-G Supertex, HV100K5-G Datasheet - Page 5

• Manufacturer Part Number: HV100K5-G
• Description: Hot Swap & Power Distribution Negative
• Manufacturer: Supertex

Specifications of HV100K5-G

• Mounting Style: SMD/SMT
• Package / Case: SOT-223
• Product: Power Distribution
• Supply Voltage (min): - 72 V
• Operating Temperature Range: - 40 C to + 85 C
• Supply Current: 1 mA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application Information
Turn On Clamp
Hotswap controllers using a MOSFET as the pass element
all include a capacitor divider from VPP to VNN through
C
external capacitor is added to the GATE of the pass element
to limit the voltage on the GATE resulting from this divider. In
those instances, if a GATE capacitor is not used the internal
circuitry is not available to hold off the GATE, and therefore
a fast rising voltage input will cause the pass element to turn
on for a moment. This allows current spikes to pass through
the MOSFET.
The HV100 includes a built-in clamp to ensure that this spuri-
ous current glitch does not occur. The built-in clamp will work
for the time constants of most mechanical connectors. There
may be applications, however, that have rise times that are
much less than 1.0µs (100’s of ns). In these instances it may
be necessary to add a capacitor from the MOSFET GATE to
source to clamp the GATE and suppress this current spike.
In these cases the current spike generally contains very little
energy and does not cause damage even if a capacitor is not
used at the GATE.
Auto-adapt Operation
The HV100 auto-adapt mechanism provides an important
function. It normalizes the hotswap period regardless of pass
element or load capacitor for consistent hotswap results. By
doing this it allows the novel short circuit mechanism to work
because the mechanism requires a known time base.
The above diagram illustrates the effectiveness of the auto-
adapt mechanism. In this example three MOSFETs with dif-
ferent C
the hotswap current, while the bottom waveform is the GATE
voltage. As can be seen, the hotswap period is normalized,
LOAD
, C
ISS
RSS
and R
and C
DSON
GS
. In most competitive solutions a large
values are used. The top waveform is
●
1235 Bordeaux Drive, Sunnyvale, CA 94089
5
the initial slope of the GATE voltage is approximately 2.5V/ms
regardless of the MOSFET, and the total hotswap period and
peak currents are a function of a MOSFET type dependent
constant multiplied by C
Typically if MOSFETs of the same type are used, the hotswap
results will be extremely consistent. If different types are used
they will usually exhibit minimal variation.
Short Circuit Protection
The HV100 provides short circuit protection by shutting down
if the Miller Effect associated with hotswap does not occur.
Specifically, if the output is shorted then the GATE will rise
without exhibiting a “flat response”. Due to the fact that we
have normalized the hotswap period for any pass element, a
timer can be used to detect if the GATE voltage rises above
a threshold within that time, indicating that a short exists. The
diagram below shows a typical turn on sequence with the load
shorted, resulting in a peak current of 4A.
The maximum current that may occur during this period can
be controlled by adding a resistor in series with the source of
the MOSFET. The lower graph shows the same circuit with
a 100mΩ resistor inserted between source and VNN. In this
case the maximum current is 25% smaller.
●
Tel: [phone]
LOAD
.
●
www.supertex.com
HV100