UC3903N UNITRODE, UC3903N Datasheet - Page 7

• Manufacturer Part Number: UC3903N
• Description: IC, SUPPLY/LINE MONITOR 18mA, 40V 18-DIP
• Manufacturer: UNITRODE

Specifications of UC3903N

• Threshold Voltage: 2.5V
• No. Of Supervisors / Monitors: 4
• Supply Voltage Range: 8V To 40V
• Reset Type: Active-Low
• Supply Current: 18mA
• Delay Time: 30ms
• Digital Ic Case Style: DIP
• No. Of Pins: 18
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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Fault Windows Scaled Independently
In many applications, it may be desirable to monitor various supply voltages, or voltage levels, with varying fault
windows. Using the reference output and external resistive dividers this is easily accomplished with the UC1903.
Figure 3
remaining inputs.
Copyright © 1999–2008, Texas Instruments Incorporated
A.
A.
Using the reference output and a resistive divider, a sense input with an independently wider fault window can be
The general purpose op-amp on the UC1903 can be used to create a sense input with an independently tighter fault
generated.
window.
and
........................................................................................................................................
Figure 4
Figure 4. UC1903 Sense Input with an Independently Tighter Fault Window
Figure 3. UC1903 Sense Input with an Independently Wider Fault Window
illustrate how the fault window at any sense input can be scaled independently of the
Supply Voltage
Fault window for the sense input, in percent, is:
Monitored
R1
R2
V
Product Folder Link(s):
S
R3
SENSE
INPUT
UC1903
±10 (V
SENSE 1-4 INPUT
2.5 V
REF.
Fault window for the Sense Input,
in percent, is:
–10 (V
for:
V
R1
R2
S
ADJ
UC1903 UC2903 UC3903
(
NOM
)
ADJ
•
) •
R
) •
1
R
R
+ R
1
R
UC1903
2
R
+ R
3
G.P. OP-AMP
2.5 V
REF.
SENSE 1-4 INPUT
2
2
+ R
2
SLUS233A – OCTOBER 1999 – REVISED SEPTEMBER 2008
= 2.5V
1
R
R
2
/(
3
R
1
+
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R
2)
,
UC1903
UC2903
UC3903
7