MAX6496EVKIT+ - Maxim Integrated Products, Inc.

General Description

The MAX6496 evaluation kit (EV kit) demonstrates a high-

voltage, overvoltage-protection circuit for automotive

applications that must survive load-dump and high-volt-

age transient conditions. This EV kit is a fully assembled

and tested surface-mount printed-circuit board (PCB).

The MAX6496 EV kit supports high-output currents of

up to 5A and can run at voltages up to 72V. An on-

board p-channel MOSFET provides reverse-battery

protection.

Features

♦5.5V to 72V Wide Supply Voltage Range

♦Up to 5A Output Current Capacity

♦Selectable Overvoltage Mode and Overvoltage-

Limiter Mode

♦Adjustable Overvoltage Threshold

♦100V Reverse-Battery Protection

Denotes lead-free and RoHS-compliant.

Evaluates: MAX6496

MAX6496 Evaluation Kit

________________________________________________________________

Maxim Integrated Products

19-0999; Rev 0; 9/07

Component List

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Ordering Information

PART TYPE

MAX6496EVKIT+ EV Kit

DESIGNATION QTY DESCRIPTION

C1, C2 2

22µF ±20%, 100V aluminum

electrolytic capacitors

Vishay 222215369229

C3 1

0.1µF ±10%, 100V X7R ceramic

capacitor (1206)

TDK C3216X7R2A104K

AVX 12061C104KAT2A

C4 0 Not installed, capacitor (1206)

J1, J2, J3 3 3-pin headers

DESIGNATION QTY DESCRIPTION

Q1 1

100V, 23A p-channel MOSFET

International Rectifier IRF9540NSPBF

Fairchild FQB22P10TM_NL

Q2 1

100V, 33A n-channel MOSFET

International Rectifier IRF540NSPBF

Fairchild FQB33N10TM_NL

R1 1 649k

±1% resistor (0805)

R2 1 49.9k

±1% resistor (0805)

R3 0 Not installed, resistor (0805)

U1 1 MAX6496ATA+ (8-pin TDFN)

— 1 PCB: MAX6496 Evaluation Kit+

SUPPLIER PHONE FAX WEBSITE

AVX Corp. 602-678-0384 602-678-0385 www.avx.com

Fairchild Semiconductor 888-522-5372 Local Rep Only www.fairchildsemi.com

International Rectifier 310-322-3331 310-322-3332 www.irf.com

TDK Corp. 847-390-4373 847-390-4428 www.component.tdk.com

Vishay 402-563-6866 402-563-6296 www.vishay.com

Component Suppliers

Note: Indicate that you are using the MAX6496 when contacting these component suppliers.

Evaluates: MAX6496

MAX6496 Evaluation Kit

2 _______________________________________________________________________________________

Quick Start

Recommended Equipment

Before beginning, the following equipment is needed:

• DC power supply (0 to 20V or above, 5A)

• Voltmeter or oscilloscope

Procedure

The MAX6496 EV kit is fully assembled and tested.

Follow the steps below to verify board operation.

Caution: Do not turn on the power supply until all

connections are completed.

1) Connect a DC power supply (0 to 20V or above, 5A

or depending on load) to IN1 and GND.

2) Connect a voltmeter or oscilloscope and a load

(if desired) to OUT and GND.

3) Make sure the J3 shunt connects pins 2-3 (overvolt-

age mode). The J1 shunt should connect pins 1-2,

and the J2 shunt should connect pins 1-2.

4) Turn on the power supply and increase the input volt-

age. The output turns on when the input voltage

reaches 5.5V. Increase the supply voltage further; the

output turns off when the input voltage reaches 17.4V.

5) The steps above can be followed for a power sup-

ply connected to IN2. The thresholds for turn-on

and turn-off are higher due to the voltage drop

across the reverse-battery protection.

Detailed Description

The MAX6496 EV kit demonstrates a high-voltage, over-

voltage-protection circuit for automotive applications

that must survive load-dump and high-voltage transient

conditions. The MAX6496 EV kit can be configured in

overvoltage mode or overvoltage-limiter mode by set-

ting jumper J3 (see Table 1 for jumper settings) and

can supply up to 5A of output current.

The MAX6496 EV kit has two positive power-supply

inputs, IN1 and IN2. Input IN2 connects to the p-chan-

nel MOSFET for reverse-battery protection; input IN1

bypasses the MOSFET.

Overvoltage Mode

In overvoltage mode, the MAX6496 monitors the input

voltage and turns off the series-pass n-channel MOSFET

(Q2) when the input voltage exceeds the programmed

threshold voltage. As soon as the input voltage drops

below the overvoltage threshold, the charge pump of

the MAX6496 fully enhances MOSFET Q2 to turn the

output back on. The voltage-divider formed by R1 and

R2 sets the threshold voltage. The resistors provided in

the MAX6496 EV kit set the threshold at 17.4V. If input

IN2 is used, the threshold will be slightly higher due to

the voltage drop across Q1.

The overvoltage threshold can be adjusted by varying

resistors R1 or R2 using the equation below:

where VOV is the desired overvoltage threshold. To

maintain threshold accuracy, R2 must be less than

250kΩ. Since the EV kit ships with R2 set at 49.9kΩ, an

easy way to change the threshold is to change R1 only,

using the formula above.

Overvoltage-Limiter Mode

In overvoltage-limiter mode, the MAX6496 monitors the

output voltage instead of the input voltage. The output

voltage is sensed through the same voltage-divider

formed by resistors R1 and R2, so the equation given for

overvoltage mode also applies to the threshold voltage

in the overvoltage-limiter mode. During an input-

overvoltage transient in this mode, the MOSFET switches

off until the output voltage falls to 95% of the threshold

voltage, and then the MOSFET switches back on. This

cycle repeats, generating a sawtooth waveform on

the output.

The minimum output voltage in overvoltage-limiter

mode depends on load current, output capacitance,

and the MOSFET’s switching period. The MAX6496 EV

kit comes with one 22µF capacitor at the output to sup-

ply the load during the time when the MOSFET is off.

Add capacitor C4 on the gate of MOSFET Q2 to

decrease the frequency of the sawtooth waveform. This

helps limit the device’s power dissipation.

Jumper Selection

Jumper J3 selects between overvoltage mode and

overvoltage-limiter mode; do not leave this jumper

unconnected. Jumper J2 controls the gate drive of

p-channel MOSFET Q1, used as reverse-battery protec-

tion. Use J2 to disconnect the MAX6496 from Q1 when

RVR

1124 12=−

⎛

⎝

⎜⎞

⎠

⎟×

Default position.

SHUNT POSITION AND FUNCTION

JUMPER 1-2 2-3

J1 U1 enabled* U1 disabled

J2 Q1 gate drive enabled* Q1 gate drive disabled

J3 Overvoltage-limiter mode Overvoltage mode*

Table 1. Jumper Settings (J1, J2, and J3)

reverse-battery protection is not used; do not leave this

jumper unconnected. Jumper J1 controls the SHDN pin

of the MAX6496 and can enable or disable the MOSFET

Q2 enhancement. Table 1 lists the jumper options.

To filter fast transients that may be present at the input

from reaching the MAX6496, cut the small trace con-

necting the two pads of R3 and place a small resistor

(10Ω, for example) on the board.

Evaluates: MAX6496

MAX6496 Evaluation Kit

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MAX6496

IN2

123

pMOS

nMOS OUT

GATEP

3OVSET

2SHDN

1IN

22μF

OPEN

0.1μF

49.9kΩ

649kΩ

OPEN

22μF

GND

IN1

GND

GATE

OUTFB

Figure 1. MAX6496 EV Kit Schematic

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

______________________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

Evaluates: MAX6496

MAX6496 Evaluation Kit

Figure 2. MAX6496 EV Kit Component Placement Guide—

Component Side

Figure 3. MAX6496 EV Kit PCB Layout—Component Side

Figure 4. MAX6496 EV Kit PCB Layout—Solder Side