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L7556AAU, L7557, L7557AAU

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Info of L7556AAU
Info of L7557
Info of L7557AAU

L7556AAU, L7557, L7557AAU Selling Leads, Datasheet

MFG:LUCENT Package Cooled:PLCC32 D/C:06+

L7556AAU, L7557, L7557AAU Datasheet download

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Part Number: L7556AAU

MFG: LUCENT

Package Cooled: PLCC32

D/C: 06+

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L7557 General Description

These electronic subscriber loop interface circuits (SLICs) are optimized for low power consumption while providing an extensive set of features.

The SLICs include an auxiliary battery input and a built-in switch. In short-loop applications, they can be used in high battery to present a high on-hook volt-age, and then switched to low battery to reduce off-hook power.

The SLICs also include a summing node for meter pulse injection to 2.2 Vrms. A spare, uncommitted op amp is included for meter pulse filtering.The switched battery is applied to the power amplifi-ers of the device. There are two ersions. The L7556 has the battery switch completely under processor control. The L7557 can automatically switch to lower battery when appropriate and includes hysteresis to avoid frequent switching. To make the switch silent, an external capacitor can be added to slow the tran-sition.

The L7556 is suited for applications serving only short loops, where a high on-hook voltage is required for compatibility with preexisting standards.

The L7557 is suited for applications where a full loop range is needed, but low short-loop power is desired. It is a much lower-cost solution than a switching reg-ulator, and also occupies much less PCB area, need-ing only a battery filter capacitor and a diode for implementation.

The device is available in a 32-pin PLCC package. It is built by using a 90 V complementary bipolar inte-grated circuit (CBIC) process.

L7557 Maximum Ratings

Stresses in excess of the Absolute Maximum Ratings can cause permanent damage to the device. These are absolute stress ratings only. Functional operation of the device is not implied at these or any other conditions in excess of those given in the operational sections of the data sheet. Exposure to Absolute Maximum Ratings for extended periods can adversely affect device reliability.

Parameter	Symbol	Value	Unit
5 V Power Supply	V_CC	7.0	V
Battery (Talking) Supply	V_BAT1	63	V
Auxiliary Battery Supply	V_BAT2	63	V
Logic Input Voltage	-	0.5 to +7.0	V
Analog Input Voltage	-	7.0 to +7.0	V
Maximum Junction Temperature	T_J	165	°C
Storage Temperature Range	T_stg	40 to +125	°C
Relative Humidity Range	R_H	5 to 95	%
Ground Potential Difference (BGND to AGND)	-	±3	V
PT or PR Fault Voltage (dc)	V_PT, V_PR	(V_BAT1 5) to +3	V
PT or PR Fault Voltage (10 x 1000 µs)	V_PT, V_PR	(V_BAT1 15) to +15	V
Current into Ring Trip Inputs	I_RTSP, I_RTSN	±240	µA

L7557 Features

Auxiliary input for second battery, and internal switch to enable its use to save power
Low active power (typical 125 mW during on-hook transmission)
Supports meter pulse injection
Spare op amp for meter pulse filtering
16 V to 60 V power supply operation
Distortion-free on-hook transmission
Convenient operating states:
- Forward powerup
- Disconnect (high impedance)
- 2-wire wink (zero loop voltage)
Adjustable supervision functions:
- Off-hook detector with longitudinal rejection
- Ground key detector
- Ring trip detector
Independent, adjustable, dc and ac parameters:
- dc feed resistance
- Loop current limit
- Termination impedance
Thermal protection

L7557 Connection Diagram

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