le75181 Zarlink Semiconductor, le75181 Datasheet - Page 14

• Manufacturer Part Number: le75181
• Description: Ringing Access Switch
• Manufacturer: Zarlink Semiconductor

APPLICATION
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1.
2.
3.
4.
5.
6.
A parallel in/parallel out data latch is integrated into the Le75181 device. Operation of the data latch is controlled by the logic level
input pin LATCH. The data input to the latch is the INPUT pin of the Le75181 device, and the output of the data latch is an internal
node used for state control.
When the LATCH control pin is at logic 0, the data latch is transparent and data control signals flow directly from INPUT, through
the data latch to state control. Any changes in INPUT will be reflected in the state of the switches.
When the LATCH control pin is at logic 1, the data latch is active—the Le75181 device will no longer react to changes at the
INPUT control pin. The state of the switches is now latched; that is, the state of the switches will remain as they were when the
LATCH input transitioned from logic 0 to logic 1. The switches will not respond to changes in INPUT as long as LATCH is held high.
Note that the TSD input is not tied to the data latch. TSD is not affected by the LATCH input. TSD input will override state control
via INPUT and LATCH.
Don’t Care
Thermal shutdown mechanism is active with T
Forcing T
Idle/Talk state.
Power ringing state.
All OFF state.
Default power up state.
INPUT
0
1
RING
Table 8. Truth Table
TIP
SD
to LOW overrides the logic input pins and forces an all OFF state.
R2
R1
1/Float
1/Float
T
Figure 7. Typical LCAS Application, A/C Versions, Idle or Talk State Shown
SD
0
Protection*
Crowbar
1
1
Tip Break Switch
Closed
Open
Open
SW3
SW4
SD
Ring
Generator
Battery
floating or HIGH.
Zarlink Semiconductor Inc.
Ring Break Switch
SW1
SW2
Closed
Open
Open
14
SCR
CKT
Trip
&
(Reference)
VBAT
Ringing Return Switch
Closed
Open
Open
BD
AD
SLIC
Ring Switch
Open
Closed
Open
3, 6
5
4