19-0999; Rev 0; 9/07
MAX6496 Evaluation Kit
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.
♦
Up to 5A Output Current Capacity
♦
Selectable Overvoltage Mode and Overvoltage-
Limiter Mode
♦
Adjustable Overvoltage Threshold
♦
100V Reverse-Battery Protection
Features
♦
5.5V to 72V Wide Supply Voltage Range
Evaluates: MAX6496
Ordering Information
PART
MAX6496EVKIT+
TYPE
EV Kit
+Denotes
lead-free and RoHS-compliant.
Component List
DESIGNATION QTY
C1, C2
2
DESCRIPTION
22µF ±20%, 100V aluminum
electrolytic capacitors
Vishay 222215369229
0.1µF ±10%, 100V X7R ceramic
capacitor (1206)
TDK C3216X7R2A104K
AVX 12061C104KAT2A
Not installed, capacitor (1206)
3-pin headers
DESIGNATION QTY
Q1
1
DESCRIPTION
100V, 23A p-channel MOSFET
International Rectifier IRF9540NSPBF
Fairchild FQB22P10TM_NL
100V, 33A n-channel MOSFET
International Rectifier IRF540NSPBF
Fairchild FQB33N10TM_NL
649kΩ ±1% resistor (0805)
49.9kΩ ±1% resistor (0805)
Not installed, resistor (0805)
MAX6496ATA+ (8-pin TDFN)
PCB: MAX6496 Evaluation Kit+
Q2
R1
R2
R3
U1
—
1
1
1
0
1
1
C3
1
C4
J1, J2, J3
0
3
Component Suppliers
SUPPLIER
AVX Corp.
Fairchild Semiconductor
International Rectifier
TDK Corp.
Vishay
PHONE
602-678-0384
888-522-5372
310-322-3331
847-390-4373
402-563-6866
FAX
602-678-0385
Local Rep Only
310-322-3332
847-390-4428
402-563-6296
www.avx.com
www.fairchildsemi.com
www.irf.com
www.component.tdk.com
www.vishay.com
WEBSITE
Note:
Indicate that you are using the MAX6496 when contacting these component suppliers.
________________________________________________________________
Maxim Integrated Products
1
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.
MAX6496 Evaluation Kit
Evaluates: MAX6496
Quick Start
Recommended Equipment
Before beginning, the following equipment is needed:
• DC power supply (0 to 20V or above, 5A)
• Voltmeter or oscilloscope
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:
⎛
V
⎞
R1
= ⎜
OV
−
1
⎟ ×
R2
⎝
1.24
⎠
where V
OV
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.
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.
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.
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.
Table 1. Jumper Settings (J1, J2, and J3)
JUMPER
J1
J2
J3
SHUNT POSITION AND FUNCTION
1-2
U1 enabled*
Q1 gate drive enabled*
Overvoltage-limiter mode
2-3
U1 disabled
Q1 gate drive disabled
Overvoltage mode*
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
*Default
position.
2
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