TSM921 TOUCHSTONE [Touchstone Semiconductor Inc], TSM921 Datasheet - Page 15

• Manufacturer Part Number: TSM921
• Description: Ultra-Low-Power, Single/Dual-Supply Comparators
• Manufacturer: TOUCHSTONE [Touchstone Semiconductor Inc]

R x C
The period value will change depending on the
leakage current and the voltage applied to the
circuit. For instance: 2MΩ x 10μF x 4. s = 92 s.
Window Detector
The schematic shown in Figure 5 is for a 4.5V
undervoltage
overvoltage threshold detector using the TSM923.
Resistor components R1, R2, and R3 can be
selected based on the threshold voltage desired
while resistors R4 and R5 can be selected based on
the hysteresis desired. Adding hysteresis to the
circuit will minimize chattering on the output when
the input voltage is close to the trip point. OUTA and
OUTB
indication and active-low overvoltage indication,
respectively. If both OUTA and OUTB signals are
ANDed together, the resulting output of the AND
gate is an active-high, power-good signal. To design
TSM921_24DS r1p0
Figure 4. Auto-Off Power Switch Operates on 2.5µA
quiescent current.
Figure 5. Window Detector
4. s
generate
threshold
the
active
detector
low
and
undervoltage
a
5.5V
the circuit, the following procedure needs to be
followed:
1. As described in the section “Hysteresis
2. Selecting R1. As the leakage current at the
3. Calculating R2 + R3. As the input voltage
4. Calculating R2. As the input voltage V
5. Calculating R3.
(TSM921 and TSM923)”, determine the
desired hysteresis and select resistors R4
and R5 accordingly. This circuit has ±5mV of
hysteresis at the input where the input
voltage V
input resistor divider.
INB- pin is less than 1nA, the current
through R1 should be at least 100nA to
minimize offset voltage errors caused by the
input leakage current. Values within 100kΩ
and
example, a 294kΩ, 1% standard value
resistor is selected for R1.
V
be 5.5V. Choose R2 + R3 as follows:
R2 + R3
the undervoltage threshold should be 4.5V.
Choose R2 as follows:
In this example, a
value resistor is selected for R2.
R3
IN
R2
294kΩ x
1.0 8MΩ
(294kΩ + 1.0 8MΩ) x
1.0 8MΩ – 1.9kΩ
1.00 MΩ
2.2kΩ
rises, the overvoltage threshold should
TSM921-TSM924
(R2 + R3) R2
1MΩ
(R1 + R2+ R3) x
IN
R1 x
1.182V +5mV
will appear larger due to the
are
5.5V
V
REF
recommended.
V
OTH
+V
1.9kΩ, 1% standard
HYS
V
1.182V 5mV
REF
1
V
UTH
4.5
1
V
HYS
Page 15
In
IN
294k
RTFDS
falls,
294k
this