HV100 查看數據表（PDF） - Supertex Inc

零件编号

产品描述 (功能)

生产厂家

HV100

3-Pin Hotswap, Inrush Current Limiter Controllers (Negative Supply Rail)

Supertex Inc 

HV100/HV101

Application Information

Turn On Clamp

Hotswap controllers using a MOSFET as the pass element all

include a capacitor divider from VPP to VNN through CLOAD, CRSS

and CGS. In most competitive solutions a large 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.

Short Circuit Protection

The HV100 and HV101 provide short circuit protection by shut-

ting 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 HV100 and HV101 include a built-in clamp to ensure

that this spurious 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 1µs (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 and HV101 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 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.

The above diagram illustrates the effectiveness of the auto-

adapt mechanism. In this example three MOSFETs with dif-

ferent CISS and RDSON values are used. The top waveform is

the hotswap current, while the bottom waveform is the gate

voltage. As can be seen, the hotswap period is normalized,

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 CLOAD.

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.

For most applications and pass elements, the HV100 and

HV101 provides adequate limiting of the maximum current to

prevent damage without the need for any external components.

The 2.5s delay of the auto-retry circuit provides time for the

pass element to cool between attempts.

5

Share Link: