TLV3011, TLV3012

SBOS300B

9

www.ti.com

FIGURE 4. The TLV3011 or TLV3012 Configured as a

Power Up Reset Circuit for the MSP430.

POWER-ON RESET

The reset circuit shown in Figure 4 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 ap-

plied, 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 will not

increase current consumption because no current flows

through the RC circuit after the supply has stabilized.

FIGURE 5. TLV3012 Configured as a Relaxation Oscillator.

V+

TLV301x

C

1

10nF

DI

R

1

1M

Ω

R

PULL-UP

(1)

10k

Ω

RESET

MSP430

1.242V

REF

NOTE: (1) Use R

The reset delay needed depends on the power-up character-

provides rapid reset if power is lost. In this example, the

RELAXATION OSCILLATOR

The TLV3012 can be configured as a relaxation oscillator as

in Figure 5 to provide a simple and inexpensive clock output.

The capacitor is charged at a rate of T = 0.69RC. It also

discharges at a rate of 0.69RC. Therefore, the period is

V+

F = 724Hz

V+

2/3 (V+)

1/3 (V+)

R

2

1M

Ω

R

1

1M

Ω

R

2

1M

Ω

R

2

1M

Ω

V

OUT

V

C

V+

t

C

1000pF

T

1

T

2

t

TLV3012