Datasheet
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Power-On Reset
V+
TLV301x
C
10 nF
1
DI
R
1
1 MΩ
R
PULLUP
(1)
10 kΩ
RESET
MSP430
1.242 V
REF
(1) Use R with the TLV3011 only.
PULLUP
+
–
Relaxation Oscillator
V+
F = 724 Hz
V+
2/3 (V+)
1/3 (V+)
R
2
1 MΩ
R
1
1 MΩ
R
2
1 MΩ
R
2
1 MΩ
V
OUT
V
C
V+
t
C
1000 pF
T
1
T
2
t
TLV3012
TLV3011-EP , TLV3012-EP
SGLS349 – OCTOBER 2006
APPLICATION INFORMATION (continued)
The reset circuit shown in Figure 25 provides a time-delayed release of reset to the MSP430 microcontroller.
Operation of the circuit is based on a stabilization time constant of the supply voltage, rather than on a
predetermined voltage value. The negative input is a reference voltage created by the internal voltage reference.
The positive input is an RC circuit that provides a power-up delay. When power is applied, the output of the
comparator is low, holding the processor in the reset condition. Only after allowing time for the supply voltage to
stabilize does the positive input of the comparator become higher than the negative input, resulting in a high
output state, releasing the processor for operation. The stabilization time required for the supply voltage is
adjustable by the selection of the RC component values. Use of a lower-valued resistor in this portion of the
circuit does not increase current consumption, because no current flows through the RC circuit after the supply
has stabilized.
Figure 25. TLV3011 or TLV3012 Configured as Power-Up Reset Circuit for the MSP430
The reset delay needed depends on the power-up characteristics of the system power supply. R
1
and C
1
are
selected to allow enough time for the power supply to stabilize. D
1
provides rapid reset if power is lost. In this
example, the R
1
× C
1
time constant is 10 ms.
The TLV3012 can be configured as a relaxation oscillator to provide a simple and inexpensive clock output (see
Figure 26 ). The capacitor is charged at a rate of T = 0.69RC and discharges at a rate of 0.69RC. Therefore, the
period is T = 1.38RC. R
1
may be a different value than R
2
.
Figure 26. TLV3012 Configured as Relaxation Oscillator
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