TS12001
allows the output of the comparator to latch to a
HIGH state under certain conditions. If
ET is set
HIGH, the COUTPP output will switch based on the
input to the comparator. When
ET is set LOW
and COUTPP is HIGH, COUTPP will remain HIGH
until
ET goes LOW. When COUTPP is initially
LOW instead, COUTPP will latch HIGH until a LOW-
to-HIGH transition occurs on the COUTPP output. In
essence, the
ET pin offers a LOW-to-HIGH
detection. However,
ET must not be left open.
The open-drain output, COUTOD, is the inverter
version of the COUTPP output. Connect
ET to
V
IN
for normal operation or to V
SS
for
ET enable.
If the SET pin is not used, it cannot be left
unconnected and should be tied to V
SS
.
Comparator
The TS12001 has an internal comparator that can
eliminate supply glitches that commonly occur when
output transitions occur. In addition, the input exhibits
±10mV of internal hysteresis in order to insure clean
output switching behavior. The outputs can swing to
within 100mV of the supply rails. The COUTPP
output can source and sink 0.1mA and 0.5mA of
current. The COUTD outputs can sink 1.4mA of
current with
V
COUTOD
= 0.78V
Internal Reference
The TS12001’s on-board 0.58V ±4.5% reference
voltage can source and sink 0.1µA and 0.1µA of
current and can drive a capacitive load less than
50pF and greater than 50nF with a maximum
capacitive load of 250nF. The higher the capacitive
load, the lower the noise on the reference voltage
and the longer the time needed for the reference
voltage to respond and become available on the
REFOUT pin. With a 250nF capacitive load, the
response time is approximately 20ms. While also
available as a separate pin as REFOUT, the
reference is tied internally to the inverting input of the
comparator.
APPLICATIONS INFORMATION
External Voltage Detector Design
Depending on the battery voltage used and the
voltage one wishes to detect, the TS12001 can be
designed accordingly. As shown in Figure 1, R1 and
R2 can be selected based on the desired voltage to
detect. Table 1. provides R1 and R2 resistor
combinations for detecting various V
IN
voltages.
Then, the second resistor value can be
evaluated using the voltage divider equation
below.
R1=
V
N
x R
V
SET
x R
V
SET
A Nanopower 1.8V Core System Voltage Detector
When power supply rails sag in any system, it is
important to alert the CPU. A CPU can be used to
detect when I/O or core system voltages sag below a
prescribed threshold as shown Figure 2. In this
circuit, a 1.8V core system voltage detector is
designed around the TS12001 providing a low battery
detect signal. R1 and R2 were selected to set a SET
voltage at 582mV so that when VCORE drops below
1.77V, the TS12001 output transitions to LOW. It is
recommended to use 1% resistors for optimal
accuracy. The circuit consumes approximately
0.75µA of current when VCORE = 1.8V.
PC Board Layout and Power-Supply Bypassing
While power-supply bypass capacitors are not
typically required, it is good engineering practice to
use 0.1uF bypass capacitors close to the device’s
power supply pins. When the power supply
impedance is high, the power supply leads are long,
or there is excessive noise on the power supply
traces. To reduce stray capacitance, it is also good
TS12001DS r1p0
RTFDS
V
IN
Threshold
R1(MΩ) R2(MΩ)
Voltage(V)
0.9
2.2
4.02
1.07
3.32
4.02
1.28
4.75
4.02
1.52
6.49
4.02
1.85
8.66
4.02
Table 1.
Resistor Combinations for Several V
IN
Threshold Voltages
The design equation for this circuit is shown
below. The SET pin voltage (V
SET
) that will
cause a HIGH-to-LOW transition on the output is
approximately 580mV. To design the circuit, R1
or R2 can be selected along with the desired
battery voltage to detect.
Page 6
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