TC54_07 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
prototyping. 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
applications, 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
TC54VX ^VOUT
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.
DS21434H-page 6
© 2007 Microchip Technology Inc.