Device
Engineering
Incorporated
DEI1028
Voltage Clamping
Circuit
385 East Alamo Drive
Chandler, AZ 85225
Phone: (480) 303-0822
Fax: (480) 303-0824
E-mail: admin@deiaz.com
FEATURES
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Protection for power electronics on 28VDC avionics or industrial power bus to
DO-160, Category Z, Abnormal Surge Voltage (DC) levels.
Controls power P-FET to clamp transient at 34V.
Small foot print (8L SOIC NB).
Wide input voltage range.
Programmable Undervoltage Lockout.
Logic compatible On/Off input.
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Stable over temperature.
Soft start delay.
GENERAL DESCRIPTION
The DEI1028 is a control circuit for a 28VDC power bus voltage clamp. It is designed for use as the front end to a 28VDC
input power supply to provide transient voltage protection. It controls the gate drive of a P-Channel power MOSFET to
linearly clamp the output during over-voltage transients. The output voltage is maintained below the clamping threshold of
35V (max) which is adequate to protect most Commercial-Off-The-Shelf switching supplies, linear regulators, and op
amps.
There is an Undervoltage Lockout feature that shuts the Power MOSFET off when the input voltage is below a user
programmed threshold. An open collector logic output annunciates the under-voltage status. There is also a logic on/off
input which may be used to control the power circuit. An external capacitor may be used to set a delay from when input
power is applied to when the MOSFET is turned on.
Table 1 Pin Definitions
Description
Pin #
Name
Figure 1: Pin
Diagram
OUTPUT. Controls the gate of the external P-channel power
MOSFET.
1
GATE
IN/OUT. Controls the soft start delay of the device. Use 0.22uF for
200ms minimum soft start time.
2
CAP
3
4
5
IN
INPUT. Power input for the DEI1028 Voltage Clamp.
UVL
NON
INPUT. Controls the under voltage lockout condition of the device.
INPUT. Logic low enables device. Logic high disables device.
OUTPUT. Open collector output. Active low when IN is below UVL
threshold.
6
NUV
7
8
GND
OUT
POWER. Ground
INPUT. Feedback to gate control from drain of Power MOSFET.
© 2017 Device Engineering Inc.
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DS-MW-01028-01-J
April 14, 2017