Datasheet

10
LTC2903-1
29031f a
APPLICATIO S I FOR ATIO
WUUU
Triple Adjustable Options (LTC2903-D1, LTC2903-E1)
LTC2903-D1 and LTC2903-E1 provide 3 adjustable in-
puts: V2, V3 and V4. The V1 threshold is 3.086V (3.3V,
5%) for option D1 and 4.675 (5V, 5%) for option E1. For
each supply monitored by an adjustable input, connect an
external resistor divider (R1 and R2) between the positive
voltage being sensed and ground. The tap point for each
divider is then connected to each adjustable input. All
adjustable inputs are compared to an internal 0.5V
reference.
Figure 3 shows how each adjustable input is configured.
Calculate the trip voltage from:
VV
R
R
TRIP
=+
⎛
⎝
⎜
⎞
⎠
⎟
05 1
1
2
.
Figure 3. Setting the Positive Adjustable Trip Point
V1 (V)
0
0
RST OUTPUT VOLTAGE (V)
0.1
0.3
0.4
0.5
0.7
0.1
0.5
0.7
29031 F02
0.2
0.6
0.4
0.9
1.0
0.2
0.3
0.6 0.8
T
A
= 25°C
V1 ONLY
COMPETITION
PART
V1 = V2 = V3
–
+
0.5V
29031 F03
V4
V
TRIP
R1
LTC2903-A1
R2
+
–
Figure 2. RST Output Voltage with a 10k Pull-Up to V1
(Enlarged Area of Detail)
current sinking ability for single supply and triple supply-
tracking applications. Figure 2 shows a detailed view of the
reset pin voltage with a 10k pull-up resistor to V1.
The LTC2903-1 supervisors derive their internal supply
voltage (V
CC
) automatically from the greater voltage on the
V1 and V2 inputs (V
CC
= V1 for options D1 and E1). With
all supply inputs above threshold, the quiescent current
drawn from V
CC
is 20µA (typ).
Supply Monitoring
The LTC2903-1 accurately monitors four inputs in a small
6-lead SOT-23 package. The low voltage reset output
includes an integrated 200ms reset delay timer. The reset
line pulls high 200ms after all voltage inputs exceed their
respective thresholds. The reset output remains low dur-
ing power-up, power-down and brownout conditions on
any of the voltage inputs.