TC54
DS21434G-page 6 2004 Microchip Technology Inc.
4.0 APPLICATIONS INFORMATION
4.1 Modifying The Trip Point, V
DET
–
Although the TC54 has a pre-programmed V
DET
–
, it is
sometimes necessary to make adjustments during pro-
totyping. This can be accomplished by connecting an
external resistor divider to a TC54, which has a V
DET
–
lower than that of V
SOURCE
(Figure 4-1).
To maintain detector accuracy, the bleeder current
through the divider should be significantly higher than
the 1 µA operating current required by the TC54. A
reasonable value for this bleeder current is 100 µA (100
times the 1 µA required by the TC54). For example, if
V
DET
–
= 2V and the desired trip point is 2.5V, the value
of R
1
+ R
2
is 25 kΩ (2.5V/100 µA). The value of R
1
+ R
2
can be rounded to the nearest standard value and
plugged into the equation of Figure 4-1 to calculate
values for R
1
and R
2
. 1% tolerance resistors are
recommended.
FIGURE 4-1: Modify trip-point of the TC54
using external resistor divider.
4.2 Other Applications
Low operating power and small physical size make the
TC54 series ideal for many voltage detector applica-
tions, such as those shown in Figures 4-2, 4-3 and 4-4.
Figure 4-2 shows a low-voltage gate drive protection
circuit that prevents overheating of the logic-level
MOSFET due to insufficient gate voltage. When the
input signal is below the threshold of the TC54VN, its
output grounds the gate of the MOSFET. Figure 4-3 and
Figure 4-4 show the TC54 in conventional voltage
monitoring applications.
FIGURE 4-2: MOSFET Low Drive
Protection.
FIGURE 4-3: Battery Voltage Monitor.
FIGURE 4-4: Power Good Monitor.
Where:
V
SOURCE
= Voltage to be monitored
(V
DET
–
) = Threshold Voltage setting of TC54
Note: In this example, V
SOURCE
must be
greater than (V
DET
–
)
V
SOURCE
R
1
R
1
R
2
+
--------------------
V
DET
-==
TC54
V
IN
V
OUT
V
SS
R
1
V
SOURCE
R
2
V
IN
V
OUT
V
SS
TC54VX
270Ω
MTP3055EL
V
CC
R
L
4.3V
V
IN
V
OUT
V
SS
BATLOW
TC54VX
+
––
V
IN
V
OUT
V
SS
Power Good
TC54VX
+
–
Pwr
Sply
