LTC2938 데이터 시트보기 (PDF) - Linear Technology
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LTC2938 Datasheet PDF : 20 Pages
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LTC2938/LTC2939
APPLICATIONS INFORMATION
A less accurate supervisor increases the required system
voltage margin and increases the probability of system
malfunction. The LTC2938 and LTC2939 ±1.5% specifica-
tion improves the reliability of the system over supervisors
with wider threshold tolerances.
Monitor Configuration
Select the LTC2938/LTC2939 input voltage combination
by placing the recommended resistive divider from VREF
to GND and connect the tap point to VPG, as shown in
Figure 2.
Table 1 offers recommended 1% resistor values for the
various modes. The rightmost column in Table 1 specifies
optimum VPG / VREF ratios (±0.01), when configuring with
a ratiometric DAC.
Upon power-up, the LTC2938 or LTC2939 enters a con-
figuration period of approximately 150μs during which
the voltage on the VPG input is sampled and the monitor
is configured to the desired input combination. Do not
add capacitance to the VPG input. Immediately after
programming, the comparators are enabled and supply
monitoring begins.
LTC2938/
LTC2939
R1
1%
VREF
VPG
R2
GND
1%
293839 F02
Figure 2. Monitor Programming
Table 1. Voltage Threshold Modes
MODE
V1 (V)
V2 (V)
0
5
3.3
1
5
3.3
2
3.3
2.5
3
3.3
2.5
4
3.3
1.8
5
5
3.3
6
5
3.3
7
3.3
1.8
8
3.3
1.8
9
3.3
1.8
10
3.3
2.5
11
3.3
2.5
12
3.3
1.8
13
3.3
1.5
14
5
3.3
15
3.3
1.2
V3 (V)
ADJ
ADJ
ADJ
ADJ
1.5
2.5
2.5
1.5
1.2
ADJ
1.8
1.8
ADJ
ADJ
1.8
ADJ
V4 (V)
ADJ
–ADJ
ADJ
–ADJ
ADJ
ADJ
1.8
1.2
ADJ
ADJ
1.5
ADJ
–ADJ
ADJ
ADJ
ADJ
R1 (kΩ)
Open
93.1
86.6
78.7
71.5
66.5
59
53.6
47.5
40.2
34.8
28
22.1
16.2
9.53
Short
R2 (kΩ)
Short
9.53
16.2
22.1
28
34.8
40.2
47.5
53.6
59
66.5
71.5
78.7
86.6
93.1
Open
VPG/VREF
0
0.094
0.156
0.219
0.281
0.344
0.406
0.469
0.531
0.594
0.656
0.719
0.781
0.844
0.906
1
293839ff
11
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