TSM931-TSM934
Bar-Graph Level Gauge
ꢀ 1.068MΩ – 61.9kΩ
A simple four-stage level detector is shown in
Figure 6 using the TSM934. Due to its high output
source capability, the TSM921 is perfect for driving
LEDs. When all of the LEDs are on, the threshold
voltage is given as VIN =(R1 + R2)/R1 volts. All other
threshold voltages are scaled down accordingly by
¾, ½, and ¼ the threshold voltage. The current
through the LEDs is limited by the output resistors.
ꢀ 1.006MΩ
In this example, a 1MΩ, 1% standard value
resistor is selected for R3.
6. Using the equations below, verify all resistor
values selected:
ꢀ
R1 + R2 + R3
VOTH ꢀ (VREF + VHYS) x
R1
Level Shifter
= 5.474V
Figure 7 provides a simple way to shift from bipolar
±5V inputs to TTL signals by using the TSM934. To
protect the comparator inputs, 10kΩ resistors are
placed in series and do not have an effect on the
performance of the circuit.
ꢀ
R1 + R2 + R3
VOTH ꢀ (VREF ꢂ VHYS) x
ꢀ 4.484V
(R1+R2)
Where the hysteresis voltage is given by:
Two-Stage Low-Voltage Detector
R5
VHYS ꢀ VREF
x
A two step, input voltage monitoring circuit can be
designed using the TSM932 as shown in Figure 8. In
this circuit, when VIN is above the LOW and FAIL
thresholds, the outputs will be HIGH. The design
procedure used to design the window detector can
be used to design this circuit.
R4
Figure 6. Bar-Graph Level Gauge
Figure 7. Level Shifter: ±5V Input into CMOS output
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TSM931_34DS r1p0
RTFDS
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