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 transmi...

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SeekIC No. : 004389427 Detail

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 ...

floor Price/Ceiling Price

Part Number:
L7557
Supply Ability:
5000

Price Break

  • Qty
  • 1~5000
  • Unit Price
  • Negotiable
  • Processing time
  • 15 Days
Total Cost: $ 0.00

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Upload time: 2024/10/30

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Product Details

Description



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



Pinout

  Connection Diagram


Specifications

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
VCC
7.0
V
Battery (Talking) Supply
VBAT1
63
V
Auxiliary Battery Supply
VBAT2
63
V
Logic Input Voltage
-
0.5 to +7.0
V
Analog Input Voltage
-
7.0 to +7.0
V
Maximum Junction Temperature
TJ
165
°C
Storage Temperature Range
Tstg
40 to +125
°C
Relative Humidity Range
RH
5 to 95
%
Ground Potential Difference (BGND to AGND)
-
±3
V
PT or PR Fault Voltage (dc)
VPT, VPR
(VBAT1 5) to +3
V
PT or PR Fault Voltage (10 x 1000 µs)
VPT, VPR
(VBAT1 15) to +15
V
Current into Ring Trip Inputs
IRTSP, IRTSN
±240
µA



Description

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

The L7557 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 L7557 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. L7557 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 L7557 is available in a 32-pin PLCC package. L7557 is built by using a 90 V complementary bipolar inte-grated circuit (CBIC) process.




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