Evaluates: MAX6495
MAX6495 Evaluation Kit
2 _______________________________________________________________________________________
Quick Start
The MAX6495 EV kit is fully assembled and tested.
Follow these steps to verify 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 VIN1 and GND.
2) Connect a voltmeter or oscilloscope and a load (if
desired) to OUT and GND.
3) Make sure the J2 shunt connects pins 1-2 (overvolt-
age-protect mode). The J4 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 17V.
5) The above steps can be followed for a power supply
connected to VIN2 or VIN3. The thresholds for turn
on and turn off for inputs VIN2 and VIN3 are higher
due to the voltage drop across the reverse-battery
protection.
Detailed Description
The MAX6495 EV kit demonstrates a high-voltage over-
voltage protection circuit for automotive applications
that must survive load dump and high-voltage transient
conditions. This EV kit can be configured in overvoltage
mode or overvoltage limiter mode by setting jumper J2
(see Table 1 for the jumper settings), and can supply
up to 5A of output current.
The MAX6495 EV kit has three positive power-supply
inputs: VIN1, VIN2, and VIN3. Inputs VIN2 and VIN3
have diode-based and p-channel MOSFET-based
reverse-battery protections, respectively, and VIN1
bypasses all reverse-battery protections.
Overvoltage Mode
In overvoltage mode, the MAX6495 monitors the input
voltage and turns off the series-pass n-channel
MOSFET (M1) when the input voltage exceeds the pro-
grammed threshold voltage. As soon as the input volt-
age drops below the overvoltage threshold, the charge
pump of the MAX6495 fully enhances MOSFET M1 to
turn the output back on. The voltage-divider formed by
R1 and R2 sets the threshold voltage. The resistors pro-
vided in the MAX6495 EV kit set the threshold at 17V. If
inputs VIN2 or VIN3 are used, this threshold will be
higher due to the voltage drop in D1 or M2.
The overvoltage threshold can be adjusted by varying
R1 or R2 using the equation below:
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.
Overvoltage Limiter Mode
In overvoltage limiter mode, the MAX6495 monitors the
output voltage instead of the input voltage. The output
voltage is sensed through the same voltage-divider
formed by R1 and R2, so the equation given for over-
voltage mode also applies to the threshold voltage in
overvoltage limiter mode. During an input overvoltage
SUPPLIER PHONE FAX WEBSITE
AVX Corp. 602-678-0384 602-678-0385 www.avx.com
Central Semiconductor Corp. 516-435-1110 516-435-1824 www.centralsemi.com
Diodes Inc. 805-446-4800 805-446-4850 www.diodes.com
Electronic Connector Service, Inc. 714-895-6351 714-894-1858 www.ecsconn.com
EPCOS 732-906-4300 732-603-5935 www.epcos.com
International Rectifier 310-322-3331 310-322-3332 www.irf.com
Murata Mfg. Co., Ltd. 770-436-1300 770-436-3030
www.murata.com
STMicroelectronics 408-452-8585 408-452-1549 www.st.com
TDK Corp. 847-390-4373 847-390-4428 www.component.tdk.com
Vishay 402-563-6866 402-563-6296 www.vishay.com
