TC54_04 Datasheet, PDF (6/16 Pages) Microchip Technology – Voltage Detector

TC54
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 R₁ + R₂ is 25 kΩ (2.5V/100 µA). The value of R₁ + R₂
can be rounded to the nearest standard value and
plugged into the equation of Figure 4-1 to calculate
values for R₁ and R₂. 1% tolerance resistors are
recommended.
V_SOURCE
R₂
V_IN
TC54
V_OUT
R₁
V_SS
VSOURCE
=
-------^R----¹--------
R1 + R2
=
VDET-
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 –)
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.
4.3V
270Ω
V_IN
V_OUT
TC54VX
V_CC
R_L
MTP3055EL
V_SS
FIGURE 4-2:
Protection.
MOSFET Low Drive
+
V_IN
–
TC54VX
V_OUT
BATLOW
V_SS
FIGURE 4-3:
Battery Voltage Monitor.
V_IN
+
Pwr
Sply
TC54VX
V_OUT
Power Good
–
V_SS
FIGURE 4-4:
Power Good Monitor.
DS21434G-page 6
 2004 Microchip Technology Inc.