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2碌A(chǔ) maximum quiescent current at 100V
General Description
The Supertex HT0638 is an integrated electronic line switch
controllable from four logic-level inputs. These devices are
intended as a replacement for mechanical hook switches and
relays in telephones, answering machines, and similar telecom-
munications equipment. They switch the positive (Tip) side of the
telephone line using control inputs that are referenced to the
negative (Ring) side of the line. In the off state, it can hold-off 375
volts. In the on state, the series resistance is 15鈩?maximum.
These devices provide adjustable current limiting via an external
sense resistor. Three of the control inputs are general purpose
and one is an override input that forces the switch to an off state
regardless of the state of the other inputs. This override input is
useful for 鈥榝lash鈥?and pulse dialing purposes. Internal pull-up/
down resistors allow the inputs to be driven from single-ended
sources, push-pull sources, or left unconnected.
The HT0638 is powered from the phone line and are especially
useful in applications where external power is not available. Due
to their low quiescent current, both of these devices exceed the
on-hook resistance requirements of EIA-470-A.
Applications
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Telephone handsets
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Fax machines
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Answering machines
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Auto-dial alarm systems
Typical Application Circuit
TPG
Tip
HKS
LS1
LS2
DP
Ring
GND
H = ON
L = OFF
CS
Charge Pump
&
Logic Control
+
15V
-
Low
Voltage
Telecom
IC
HT0640
TP
For additional information, refer to application note
AN-H32.
08/23/02
Supertex Inc. does not recommend the use of its products in life support applications and will not knowingly sell its products for use in such applications unless it receives an adequate "products liability
indemnification insurance agreement." Supertex does not assume responsibility for use of devices described and limits its liability to the replacement of devices determined to be defective due to
workmanship. No responsibility is assumed for possible omissions or inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications, refer to the
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Supertex website: http://www.supertex.com. For complete liability information on all Supertex products, refer to the most current databook or to the Legal/Disclaimer page on the Supertex website.
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