SIDB766761 Datasheet, PDF (1/5 Pages) Vishay Siliconix – Temperature Sensing MOSFET Evaluation Board

SiDB766761
Vishay Siliconix
Temperature Sensing MOSFET Evaluation Board
FEATURES
D Turns Off MOSFET Before T_J Exceeds 175_C Rating
D 5-V Logic Level Operation of Control Circuit
D 12-V Battery Level Operation of Power MOSFET Circuit
D Sense Diode Bias Current, I_F = 250 mA
D Built-In Hysterisis to Ensure Jitter Free Operation
D Cyclic Operation of MOSFET (Turn-On and Turn-Off)
Under Continuous Fault Condition
D Flexibility to Set MOSFET Turn-Off Temperature
ORDERING INFORMATION: SiDB766761
DESCRIPTION
The Vishay Siliconix SUB60N04-15LT, temperature sensing
MOSFET, provides the capabilities to sense the junction
temperature, T_J, and implement self-protection in a control
circuit. An electrically isolated poly-silicon diode, which is
located in the close proximity to MOSFET junction on the same
die, facilitates temperature sensing. The forward voltage drop
of sense diode has a negative temperature co-efficient of
approximately −2mV/_C. In other words, the forward voltage
drop of the sense diode is inversely proportional to the
MOSFET junction temperature.
This evaluation board demonstrates the self-protection feature in
a control circuit, using SUB60N04-15LT, the temperature sensing
MOSFET. The cyclic turn-off and turn-on of the MOSFET under
the fault condition protects it from catastrophic failure.
The appendix includes, a schematic diagram, test setup,
bill-of-materials, and PCB layouts. Using this information, one
can incorporate the basic control scheme described here, in
any core system design of an application.
The demonstration board layout is available in Gerber file format. Contact your Vishay Siliconix sales representative/ distributor for a copy.
CIRCUIT DESCRIPTION
The schematic diagram shown in Appendix (A) is a simple
comparator circuit that uses a low cost op-amp, LMV321. This
IC is identified as “U1.” The op-amp output Pin 4 provides gate
drive approximately 4.8 V through resistor R6 to the
temperature sensing MOSFET, Q1. The latter in turn controls
the “load” connected between its drain, Pin 3, and +12 V. The
voltage divider, resistors R1 and R2, establishes reference
voltage V_REF = 490 mV. 5-V logic level input at the INPUT
terminal provides the bias current, I_F = 250 mA, for the sense
diode on Pins 2 and 4 of Q1. The op-amp is configured for
non-inverting mode by connecting the sense diode forward
voltage drop to Pin 1, the “+” input through resistors R7. The
feedback resistor R4 establishes 20-mV hysteresis on R7 to
ensure jitter free operation. Resistor R5 facilitates monitoring
of gate drive signal. Resistor R_G when connected to the
MOSFET gate via jumper J2, cuts down the MOSFET gate
drive to 2.8 V and shifts the MOSFET operation to linear mode.
The peripheral capacitors C1 through C5 are for power supply
filter and noise suppression.
S
D²PAK-5L
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T₁
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D₂
T₂
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Document Number: 72800
18-Mar-04
D
P-Channel MOSFET
www.vishay.com
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