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| 型号： | HT9142-20TSSOP-A |
| 英文描述： | Analog IC |
| 中文描述： | 模拟IC |
| 文件页数： | 4/8页 |
| 文件大小： | 97K |
| 代理商： | HT9142-20TSSOP-A |
HT9142
Rev. 1.10
4
July 31, 2002
Functional Description
Battery-saving function
The battery-saving function is controlled by the pin BS
and the battery consumption is minimized by reducing
the current consumption. If the pin is logic LOW, the
HT9142 enters the battery-saving mode, otherwise
HT9142 is in normal operation state.
FSK NRZ output
The HT9142 has two built-in operation amplifiers. One
of these operation amplifiers is connected inside the IC
to the NRZ comparator. The NRZ comparator can out-
put the input signal waveform as a square wave. The
NRZ comparator output is an open collector. If the IC in-
terfaces with CMOS devices, the possible connection is
shown below.
Quick charge-discharge circuit
If an FSK signal inputs during the brief transition from
battery-saving state to normal operation state, the time
that the pin FSKR arrives at the reference voltage is
delayed by a time constant determined by the capacitor
connected to the pin FSKR and the internal resistor.
Sometimes, the output signal becomes erroneous due
to some error in the comparator input voltage. Such a
case could be avoided by quickly charging or discharg-
ing the capacitor connected to the pin FSKR . By using
the quick charge-discharge circuit, the delay time for the
FSKR pin to be of the same level with the LPFO pin
could be minimized, hence, erroneous FSK NRZ output
signal is prevented.
Battery low alarm function
In case the HT9142 is battery powered, when the power
supply voltage goes low to about 1.1V, the output of the
pin ALM 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 fig-
ure below, the output REGO could be used constantly
as 1.0V regulator output. At the battery-saving mode,
the regulator is turned OFF.
Local oscillator circuit
The HT9142 local oscillator circuit is of Colpitts type os-
cillator composed of internal emitter follower circuit and
an external X tal. The transistor is connected externally
as shown in the figure below. Resistor
needed to increase the current of the local oscillator cir-
cuit in order to compose the overtone oscillator and im-
prove its stability. It is recommended that the resistor be
connected between OSCI and REGO to provide bat-
tery-saving mode.
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| HT9170 | 制造商:HOLTEK 制造商全称:Holtek Semiconductor Inc 功能描述:DTMF Receiver |
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