HT9011 datasheet(5/7 Pages) HOLTEK

5 / 7 page

HT9011

March 1, 2000

Preliminary

Functional Description

Battery-saving function

The battery-saving function is controlled by the

pin ²BS² and the battery consumption is mini-

mized by reducing the current consumption. If

the pin is logic LOW, the HT9011 enters the

battery-saving mode, otherwise HT9011 is in

normal operation state.

FSK NRZ output

The HT9011 has two built-in operation amplifi-

ers. One of these operation amplifiers is con-

nected inside the IC to the NRZ comparator.

The NRZ comparator can output the input sig-

nal waveform as a square wave. The NRZ com-

parator output is an open collector. If the IC

interfaces with CMOS devices, the possible con-

nection is shown below.

Quick charge-discharge circuit

If an FSK signal inputs during the brief transi-

tion from battery-saving state to normal opera-

tion state, the time that the pin ²FSKR² arrives

at the reference voltage is delayed by a time

constant determined by the capacitor connected

to the pin ²FSKR² and the internal resistor.

Sometimes, the output signal becomes errone-

ous due to some error in the comparator input

voltage. Such a case could be avoided by quickly

charging or discharging the capacitor con-

nected to the pin ²FSKR². By using the quick

charge-discharge circuit, the delay time for the

²FSKR² pin to be of the same level with the

²LPFO² pin could be minimized, hence, errone-

ous FSK NRZ output signal is prevented.

Battery low alarm function

In case the HT9011 is battery powered, when

the power supply voltage goes low to about 1.1V,

the output of the pin ²ALM² rises up to about

1.1V and the battery voltage can be monitored

by other devices. The output is an open collector

similar to FSK NRZ output.

Constant voltage regulator for external part

power supply

Externally connecting the transistor as shown

in the figure below, the output ²REGO² could be

used constantly as 1.0V regulator output. At

the battery-saving mode, the regulator is

turned OFF .

Local oscillator circuit

The HT9011 local oscillator circuit is of Colpitts

type oscillator composed of internal emitter fol-

lower circuit and an external X¢tal. The transis-

tor is connected externally as shown in the

figure below. Resistor ²R² may be needed to in-

crease the current of the local oscillator circuit

in order to compose the overtone oscillator and

improve its stability. It is recommended that

the resistor be connected between OSCI and

REGO to provide battery-saving mode.

V CC fo r

CM O S I C

F SKO

V CC

1. 5V

V CC

1. 0 m F

R E GO

R E GC

2N 3906

Vr e g

OS C I

OS C O

22k W

RE G O

21. 8 55M H z

56pF

47pF

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