LTC2914IDHC-2 데이터 시트보기 (PDF) - Linear Technology
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LTC2914IDHC-2 Datasheet PDF : 16 Pages
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LTC2914
APPLICATIONS INFORMATION
For positive supply monitoring, Vn is the desired nominal
operating voltage, In is the desired nominal current through
the resistive divider, VOV is the desired overvoltage trip
point and VUV is the desired undervoltage trip point.
For negative supply monitoring, to compensate for the 1V
reference, 1V must be subtracted from Vn, VOV and VUV
before using each in the following equations.
1. Choose RA to obtain the desired OV trip point
RA is chosen to set the desired trip point for the
overvoltage monitor.
RA
=
0.5V
In
•
Vn
VOV
(1)
2. Choose RB to obtain the desired UV trip point
Once RA is known, RB is chosen to set the desired trip
point for the undervoltage monitor.
RB =
0.5V
In
•
Vn
VUV
– RA
(2)
3. Choose RC to Complete the Design
Once RA and RB are known, RC is determined by:
RC =
Vn
In
– RA – RB
(3)
If any of the variables Vn, In, VUV or VOV change, then each
step must be recalculated.
Positive Voltage Monitor Example
A positive voltage monitor application is shown in Figure 3.
The monitored voltage is a 5V ±10% supply. Nominal cur-
rent in the resistive divider is 10μA.
V1
VCC
5V ±10%
5V
RC
442k
RB
10.2k
RA
45.3k
VCC
VH1
OV
LTC2914
VL1
UV
SEL
GND
2914 F03
Figure 3. Positive Supply Monitor
1. Find RA to set the OV trip point of the monitor.
RA
=
0.5V
10µA
•
5V
5.5V
45.3k
2. Find RB to set the UV trip point of the monitor.
RB
=
0.5V
10µA
•
5V
4.5V
– 45.3k 10.2k
3. Determine RC to complete the design.
RC
=
5V
10µA
–
45.3k
10.2k 442k
Negative Voltage Monitor Example
A negative voltage monitor application is shown in Figure 4.
The monitored voltage is a –5V ±10% supply. Nominal
current in the resistive divider is 10μA. For the negative
case, 1V is subtracted from Vn, VOV and VUV.
1. Find RA to set the OV trip point of the monitor.
RA
=
0.5V
10µA
•
–5V – 1V
–5.5V – 1V
46.4k
2. Find RB to set the UV trip point of the monitor.
RB
=
0.5V
10µA
•
5V – 1V
4.5V – 1V
46.4k 8.45k
3. Determine RC to complete the design.
RC =
–5V – 1V
10µA
46.4k 8.45k 549k
VCC
5V
RA
46.4k
RB
8.45k
RC
549k
V3
–5V ±10%
VCC
REF
OV
LTC2914
VH3
UV
VL3
SEL
GND
2914 F04
Figure 4. Negative Supply Monitor
2914fa
9
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