LTC2938 LINER [Linear Technology], LTC2938 Datasheet - Page 11

• Manufacturer Part Number: LTC2938
• Description: Confi gurable 4- and 6-Supply Monitors with Watchdog Timer
• Manufacturer: LINER [Linear Technology]

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% specifi ca-
tion improves the reliability of the system over supervisors
with wider threshold tolerances.
Monitor Confi guration
Select the LTC2938/LTC2939 input voltage combination
by placing the recommended resistive divider from V
to GND and connect the tap point to V
Figure 2.
Table 1 offers recommended 1% resistor values for the
various modes. The rightmost column in Table 1 specifi es
optimum V
a ratiometric DAC.
Table 1. Voltage Threshold Modes
PG
MODE
/ V
10
11
12
13
14
15
0
1
2
3
4
5
6
7
8
9
REF
ratios (±0.01), when confi guring with
V1 (V)
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
5
5
5
5
5
V2 (V)
3.3
3.3
2.5
2.5
1.8
3.3
3.3
1.8
1.8
1.8
2.5
2.5
1.8
1.5
3.3
1.2
PG
, as shown in
V3 (V)
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
1.5
2.5
2.5
1.5
1.2
1.8
1.8
1.8
REF
Upon power-up, the LTC2938 or LTC2939 enters a con-
fi guration period of approximately 150μs during which
the voltage on the V
is confi gured to the desired input combination. Do not
add capacitance to the V
programming, the comparators are enabled and supply
monitoring begins.
V4 (V)
–ADJ
–ADJ
–ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
ADJ
1.8
1.2
1.5
R1 (kΩ)
293839 F02
Short
Figure 2. Monitor Programming
Open
93.1
86.6
78.7
71.5
66.5
53.6
47.5
40.2
34.8
22.1
16.2
9.53
59
28
LTC2938/
LTC2939
LTC2938/LTC2939
PG
V
GND
V
REF
PG
input is sampled and the monitor
R2 (kΩ)
Short
Open
9.53
16.2
22.1
34.8
40.2
47.5
53.6
66.5
71.5
78.7
86.6
93.1
PG
28
59
1%
R1
input. Immediately after
R2
1%
V
PG
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
/V
0
1
REF
11
293839ff