19-4002; Rev 2; 12/06
MAX6495 Evaluation Kit
General Description
The MAX6495 evaluation kit (EV kit) demonstrates a
high-voltage overvoltage protection circuit for automo-
tive applications that must survive load dump and high-
voltage transient conditions. This EV kit is a fully assem-
bled and tested surface-mount board.
This EV kit supports high output currents of up to 5A,
operates at voltages up to 72V, and withstands temper-
atures ranging from -40°C to +105°C. Two alternate
voltage inputs implement two different schemes for
reverse-battery protection.
o
Up to 5A Output Current Capacity
o
Selectable Overvoltage Mode and Overvoltage
Limiter Mode
o
Adjustable Overvoltage Threshold
o
100V Reverse-Battery Protection
Features
o
5.5V to 72V Wide Supply Voltage Range
Evaluates: MAX6495
Ordering Information
PART
MAX6495EVKIT
TEMP RANGE
-40°C to +105°C
IC PACKAGE
6 TDFN-EP*
*EP
= Exposed paddle.
Component List
DESIGNATION
C1, C7
C2, C8–C12
C3
C6
C13
D1
QTY
2
0
1
1
1
1
DESCRIPTION
22µF, 100V aluminum electrolytic
capacitors
Vishay 222215369229
Not installed, capacitors
Not installed, capacitor (1206)
0.1µF, 100V X7R ceramic capacitor
TDK C3216X7R2A104K or
AVX 12061C104KAT2A
Not installed, electrolytic capacitor
8A/100V Schottky diode
International Rectifier 8TQ100S or
ST Microelectronics STPS8H100G
60V, 600W TVS diode
Diodes SMBJ54A or
Fairchild SMBJ54A
18V zener diode
Central Semi CMPZ5248B or
Diodes MMBZ5248BT
Not installed, optional TVS diode
(DO-15)
M2
R1
R2
R4
R5
R6
U1
—
1
1
1
1
1
1
1
1
DESIGNATION
J1
J2, J3, J4
M1
QTY
0
3
1
DESCRIPTION
Not installed, 2-pin header
3-pin headers
100V, 33A n-channel MOSFET
International Rectifier IRF540NS or
Fairchild FQB33N10
100V, 23A p-channel MOSFET
International Rectifier IRF9540NS or
Fairchild FQB22P10
649kΩ ±1% resistor (0805)
49.9kΩ ±1% resistor (0805)
Not installed, resistor (0805)
100kΩ ±1% resistor (0805)
2.2MΩ ±1% resistor
MAX6495ATT (6-pin TDFN)
PCB: MAX6495EVKIT
D2
1
D3
1
D4
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
MAX6495 Evaluation Kit
Evaluates: MAX6495
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.
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:
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.
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
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
Component Suppliers
SUPPLIER
AVX Corp.
Central Semiconductor Corp.
Diodes Inc.
Electronic Connector Service, Inc.
EPCOS
International Rectifier
Murata Mfg. Co., Ltd.
STMicroelectronics
TDK Corp.
Vishay
PHONE
602-678-0384
516-435-1110
805-446-4800
714-895-6351
732-906-4300
310-322-3331
770-436-1300
408-452-8585
847-390-4373
402-563-6866
FAX
602-678-0385
516-435-1824
805-446-4850
714-894-1858
732-603-5935
310-322-3332
770-436-3030
408-452-1549
847-390-4428
402-563-6296
WEBSITE
www.avx.com
www.centralsemi.com
www.diodes.com
www.ecsconn.com
www.epcos.com
www.irf.com
www.murata.com
www.st.com
www.component.tdk.com
www.vishay.com
Note:
Indicate that you are using the MAX6495 when contacting these component suppliers.
2
_______________________________________________________________________________________
MAX6495 Evaluation Kit
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 MAX6495 EV
kit comes with one 22µF capacitor at the output to sup-
ply the load during the time when the MOSFET is off.
Connect the optional electrolytic capacitor C13 (150µF,
100V) to support load currents higher than 0.5A when
the EV kit operates in overvoltage limiter mode.
Add capacitor C3 on the gate of MOSFET M1 to
decrease the frequency of the sawtooth waveform. This
process helps limit the device’s power dissipation.
Three-pin jumper J2 selects between overvoltage mode
and overvoltage limiter mode; do not leave this jumper
unconnected. Three-pin jumper J3 controls the gate
drive of p-channel MOSFET M3 used as a reverse-bat-
tery protection. Use J3 to disconnect resistor R5 when
M3 is not used to avoid supply leakage through R5.
Three-pin jumper J4 controls the
SHDN
pin of the
MAX6495 and can enable or disable the MOSFET M1
enhancement. Table 1 lists the jumper options.
Evaluates: MAX6495
Table 1. Jumper Function
JUMPER
J1
J2
SHUNT POSITION AND FUNCTION
1-2
Overvoltage mode*
M2 gate drive is
disabled*
U1 is enabled*
2-3
Overvoltage limiter mode
M2 gate drive is enabled
U1 is disabled
Shorted: RC input filter disabled*
Jumper Selection
To filter fast transients that may be present at the input
from reaching the MAX6495, place a small resistor, R4,
(10Ω, for example) on the board, and cut jumper J1.
J3
J4
*Default
configuration.
_______________________________________________________________________________________
3
Evaluates: MAX6495
MAX6495 Evaluation Kit
Figure 1. MAX6495 EV Kit Schematic
4
M1
IRF540
OUT
D1
8TQ100S-IS
D2
SMBJ54A
D4
OPEN
C2
OPEN
C10
OPEN
C11
OPEN
C9
OPEN
C8
OPEN
C7
22µF
100V
C1
22µF
100V
C12
OPEN
C13
OPEN
M2
IRF9540
D3
18V
R6
2.2MΩ
1
IN
U1 OUTFB
6
R1
649kΩ
J1
R4
OPEN
J2
J2
1 2 3
C3
OPEN
GND
3 2 1
J3
C6
0.1µF
100V
VIN1
VIN2
VIN3
MAX6495
2
SHDN
OVSET
GND
4
GATE
5
GND
3
R2
49.9kΩ
_______________________________________________________________________________________
1
J4 2
3
R5
100kΩ
MAX6495 Evaluation Kit
Evaluates: MAX6495
Figure 2. MAX6495 EV Kit Component Placement Guide—Component Side
_______________________________________________________________________________________
5
嵌入式系统
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
