HV100K6-G - Supertex, Inc.

HV100/HV101

3-Pin Hotswap, Inrush Current Limiter Controllers

(Negative Supply Rail)

A092605

Features

❑ 33% Smaller than SOT-232

❑ Pass Element is Only External Part

❑ No Sense Resistor required

❑ Auto-Adapt* to Pass Element

❑ Short Circuit Protection*

❑ UV & POR Supervisory Circuits

❑ 2.5s Auto Retry

❑ ±10V to ±72V Input Voltage Range

❑ 0.6mA Typical Operating Supply Current

❑ Built in Clamp for AC Path Turn On Glitch

Applications

❑ -48V Central Ofﬁ ce Switching (line cards)

❑ +48V Server Networks

❑ +48V Storage Area Networks

❑ +48V Peripherals, Routers, Switches

❑ +24V Cellular and Fixed Wireless (bay stations,

line cards)

❑ +24V Industrial Systems

❑ +24V UPS Systems

❑ -48V PBX & ADSL Systems (line cards)

❑ Distributed Power Systems

❑ Powered Ethernet for VoIP

General Description

The HV100/HV101 are 3-pin hotswap controllers available in

the SOT-223 package, which require no external components

other than a pass element. The HV100/HV101 contains many

of the features found in hotswap controllers with 8 pins or more,

and which generally require many external components. These

features include undervoltage (UV) detection circuits, power on

reset (POR) supervisory circuits, inrush current limiting, short

circuit protection, and auto-retry. In addition, the HV100/HV101

use a patent pending mechanism to sample and adapt to any

pass element, resulting in consistent hotswap proﬁ les without

any programming.

The only difference between the HV100 and the HV101 is the

internally set undervoltage (UV) threshold.

Typical Application Circuit and Waveforms

-48V

GND

GATE

VPP

VNN

HV100 DC/DC

Converter

+5V

COM

IRF530

400F

UV Options Package Options

3-Pin SOT-223

34V HV100K5/ HV100K5-G

14V HV101K5/ HV101K5-G

Ordering Information

-G indicates package is RoHS compliant (‘Green’)

*Patents Pending

1IRF530 is a Trademark of International Rectiﬁ er Corporation

2MLP3x2 Package Version compared to 3mmx3mm SOT-23-6

A092605

HV100/HV101

Absolute Maximum Ratings

DC Electrical Characteristics (VH = VDD = 12V, VL = VSS = GND = 0V, VOE = 3.3V, TJ = 25°C)

Sym. Parameter Min. Typ. Max. Units Conditions

Supply (Referenced to VPP pin)

VNN Supply Voltage -72 - UV V -

INN Supply Current - 0.6 1.0 mA VNN = -48.0V

UV Control (Referenced to VNN pin)

VUVL UV Threashold (High to Low) 30 34 38 V HV100

12.3 14 15.7 V HV101

VUVH UV Hysteresis - 3 - V HV100

- 1 - V HV101

Gate Drive Output (Referenced to VNN pin)

VGATE Maximum Gate Drive Voltage 10 12 14 V -

SRGATE Initial Slew Rate 1.5 - 3.75 V/ms CGATE = 1nF

IGATEDOWN Gate Drive Pull-Down Current (Sinking) 8 16 - mA VGATE = 1.0V; VPP = 11.5V

IPULLUP Post Hot Swap Pull-Up Current 6 11 - μA VGATE = 6.0V

Timing Control (Referenced to VNN pin)

tPOR Insertion POR Delay 1.5 3.5 5.5 ms -

tARD Auto Restart Delay 1.25 2.5 3.75 s -

Example Electrical Results (Using IRF530)

ILIM Max Inrush Current During Hotswap - 1.4 - A IRF530 external MOSFET, CLOAD = 100μF

ILIM Max Inrush Current During Hotswap - 2.5 - A IRF530 external MOSFET, CLOAD = 200μF

ILIM Max Inrush Current During Hotswap - 3.1 - A IRF530 external MOSFET, CLOAD = 300μF

ISHORT Max Current Into a Short - 4.0 - A IRF530 external MOSFET, RLOAD = <<1.5

tSHORT Shorted Load Detect Time - 1.0 ms IRF530 external MOSFET, RLOAD = <<1.5

ΔGATE Initial Rate of Rise of Gate - 2.5 - V/ms IRF530 external MOSFET, any CLOAD

tHS Hot Swap Period to Full Gate Value - 12.5 - ms IRF530 external MOSFET, any CLOAD

Pinout

123

VNN GATE

VPP

Top View

SOT-223

VPP Input Voltage -0.3V - 75.0V

Operating Ambient Temperature Range -40oC to +85oC

Operating Junction Temperature Range -40oC to +125oC

Storage Temperature Range -65oC to +150oC

Pin Description

VPP Positive voltage power supply to the circuit.

VNN Negative voltage power supply to the circuit.

Gate Gate driver output for the external n-Channel MOSFET

A092605

HV100/HV101

Functional Block Diagram

Regulator

UVLO

POR

Timer

Reference

Generator

Logic

Restart

Timer GATE

VPP

VNN

Functional Description

Insertion into Hot Backplanes

Telecom, data network and some computer applications

require the ability to insert and remove circuit cards from

systems without powering down the entire system. Since all

circuit cards have some ﬁ lter capacitance on the power rails,

which is especially true in circuit cards or network terminal

equipment utilizing distributed power systems, the insertion

can result in high inrush currents that can cause damage to

connector and circuit cards and may result in unacceptable

disturbances on the system backplane power rails.

The HV100/HV101 are designed to facilitate the insertion

and removal of these circuit cards or connection of terminal

equipment by eliminating these inrush currents and powering

up these circuits in a controlled manner after full connector

insertion has been achieved. The HV100/HV101 are intended

to provide this control function on the negative supply rail.

Description of Operation

On initial power application the high input voltage internal

regulator seeks to provide a regulated supply for the internal

circuitry. Until the proper internal voltage is achieved all circuits

are held reset by the internal UVLO and the gate to source

voltage of the external N-channel MOSFET is held off. Once

the internal regulator voltage exceeds the UVLO threshold,

the input undervoltage detection circuit (UV) senses the input

voltage to conﬁ rm that it is above the internally programmed

threshold. If at any time the input voltage falls below the UV

threshold, all internal circuitry is reset and the GATE output

is pulled down to VNN. UVLO detection works in conjunction

with a power on reset (POR) timer of approximately 3.5ms to

overcome contact bounce. Once the UVLO is satisﬁ ed the

gate is held to VNN until a POR timer expires. Should the UV

monitor toggle before the POR timer expires, the POR timer

will be reset. This process will be repeated each time UVLO

is satisﬁ ed until a full POR period has been achieved.

After completion of a full POR period, the MOSFET gate Auto-

Adapt operation begins. A reference current source is turned

on which begins to charge an internal capacitor generating

a ramp voltage which rises at a slew rate of 2.5 V/ms. This

reference slew rate is used by a closed loop system to gen-

erate a GATE output current to drive the gate of the external

N-channel MOSFET with a slew rate that matches the refer-

ence slew rate. Before the gate crosses a reference voltage,

which is well below the VTH of industry standard MOSFETs,

the pull-up current value is stored and the Auto-Adapt loop

is opened. This stored pull-up current value is used to drive

the gate during the remainder of the hot swap period. The

result is a normalization with CISS , which for most MOSFETs

scales with CRSS.

The MOSFET gate is charged with a current source until it

reaches its turn on threshold and starts to charge the load

capacitor. At this point the onset of the Miller Effect causes

the effective capacitance looking into the gate to rise, and

the current source charging the gate will have little effect on

the gate voltage. The gate voltage remains essentially con-

stant until the output capacitor is fully charged. At this point

the voltage on the gate of the MOSFET continues to rise to

a voltage level that guarantees full turn on of the MOSFET.

It will remain in the full on state until an input under voltage

condition is detected.

If the circuit attempts turn on into a shorted load, then the Miller

Effect will not occur. The gate voltage will continue to rise

essentially at the same rate as the reference ramp indicating

that a short circuit exists. This is detected by the control circuit

and results in turning off the MOSFET initiating a 2.5 second

delay, after which a normal restart is attempted.

If at any time during the start up cycle or thereafter, the input

voltage falls below the UV threshold the GATE output will

be pulled down to VNN, turning off the N-channel MOSFET

and all internal circuitry is reset. A normal restart sequence

will be initiated once the input voltage rises above the UVLO

threshold plus hysteresis.

A092605

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.

The HV100/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/HV101 Auto-adapt mechanism provides an impor-

tant 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 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.

Short Circuit Protection

The HV100/HV101 provide short circuit protection by shutting

down if the Miller Effect associated with hotswap does not oc-

cur. Speciﬁ cally, if the output is shorted then the gate will rise

without exhibiting a “ﬂ at 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.

For most applications and pass elements, the HV100/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.

A092605

HV100/HV101

Auto-Retry

Not only does the HV100/HV101 provide short circuit protection

in a 3-pin package, it also includes a 2.5s built in auto-restart

timer. The HV100/HV101 will continuously try to turn on the

system every 2.5s, providing sufﬁ cient time for the pass ele-

ment to cool down after each attempt.

Calculating Inrush Current

As can be seen in the diagram below, for a standard pass ele-

ment, the HV100/HV101 will normalize the hotswap time period

against load capacitance. For this reason the current limit will

increase with increasing value of the load capacitance.

Inrush can be calculated from the following formula:

IINRUSH(PEAK) = (CISS / CRSS) * 2.5e3 * CLOAD

This is a surprisingly consistent result because for most MOS-

FETs of a particular type the ratio of CISS / CRSS is relatively

constant (though notice from the plot that there is some varia-

tion) even while the absolute value of these and other quantities

vary. Based on this, the inrush current will vary primarily with

CLOAD. This makes designing with the HV100/HV101 particularly

easy because once the pass element is chosen, the period

is ﬁ xed and the inrush varies with CLOAD only.

Programming the HV100/HV101

The HV100/HV101 require no external components other

than a pass element to provide the functionality described

thus far. In some applications it may be useful to use external

components to adjust the maximum allowable inrush current,

adjust UVLO, or to provide additional gate clamping if the

supply rails have rise times below 1ms.

All of the above are possible with a minimum number of ex-

ternal components.

i) To adjust inrush current with an external component

simply connect a capacitor (CFB) from drain to gate of the

MOSFET. The inrush calculation then becomes:

IINRUSH(PEAK) = (CFB + CISS)/(CRSS + CFB) * 2.5e3 * CLOAD

Note that a resistor (approximately 10KΩ) needs to be

added in series with CFB to create a zero in the feedback

loop and limit the spurious turn on which is now enhanced

by the larger divider element.

ii) To increase undervoltage lockout simply connect a Zener

diode in series with the VPP pin.

iii) If the VPP rises particularly fast (>48e6V/s) then it may

be desirable to connect a capacitor from gate to source

of the MOSFET to provide a path for the power applica-

tion transient spike, which is now too fast for the internal

clamping mechanism.

iv) To limit the peak current during a short circuit, a resistor

in series with the source of the MOSFET may help.

Implementing PWRGD Control

Due to the HV100/HV101’s small footprint, it is possible to cre-

ate an open drain PWRGD signal using external components

and still maintain a size comparable with the smallest hotswap

controllers available elsewhere. To accomplish this an external

MOSFET may be used in conjunction with the gate output.

Simply use a high impedance divider (10MΩ) sized so that the

open drain PWRGD MOSFET threshold will only be reached

once the HV100/HV101’s gate voltage rises well above the

current limit value required by the external MOSFET pass

device. Alternatively a Zener diode between the gate output

and the PWRGD MOSFET gate set at a voltage higher than

the maximum pass element Vt will also work.

HV100

PWGRD

Doc.# DSFP - HV100_HV101

A092605

HV100/HV101

Powered Ethernet (Power-Over-LAN) / VoIP Solutions

HV101 Used as a UVLO & Load Switch

DC / DC Converter

3.3V/5V

Powered Device (PD)

PHY

HV101

VPP

GATE

VNN

3_Lead SOT-223 (K5) Package

0.12 ± 0.004

(3.05 ± 0.10)

0.256 ± 0.008

(6.50 ± 0.20)

0.138 ± 0.008

(3.50 ± 0.20)

0.2755 ± 0.0115

(7.00 ± 0.30)

0.0905

(2.30) TYP.

0.037 ± 0.004

(0.95 ± 0.10)

0.0635 ± 0.0035

(1.60 ± 0.10)

0.0024 ± 0.0016

(0.06 ± 0.04) 0.0295 ± 0.0035

(0.75 ± 0.10)

0.181

(4.60) TYP.

0.067 ± 0.004

(1.20 ± 0.10)

e Max

0.012 ± 0.002

(0.30 ± 0.05)

Dimensions in Inches

(Dimensions in Millimeters)

Measurement Legend =

Note: Circle (e.g. B ) indicates JEDEC Reference.