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Microchip Technology LE7942B-1DJC
- Part No.:
- LE7942B-1DJC
- Manufacturer:
- Microchip Technology
- Category:
- Telecom
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
LE7942B-1DJC.pdf
- Description:
- IC TELECOM INTERFACE 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:4,528
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Product details
Overview
LE7942B-1DJC from Zarlink Semiconductor is a high-voltage subscriber line interface circuit (SLIC) designed for PBX and key telephone system (KTS) applications. It delivers programmable constant-current feed, –19 V to –58 V battery operation, 500× receive current gain, on-chip switching regulator support, and ground-key detection with dedicated GKFIL pin for external noise-filter capacitor.
For engineers reviewing the LE7942B-1DJC datasheet, LE7942B-1DJC pinout, LE7942B-1DJC application, or LE7942B-1DJC equivalent, this device serves as a fully integrated SLIC solution for analog telephony line cards requiring polarity reversal, loop detection, relay drivers (RINGOUT/TESTOUT), and low standby power in commercial temperature range (0°C to +70°C).
Technical Context
The LE7942B-1DJC implements a dual-path analog front-end with independent A(TIP) and B(RING) power amplifiers, driven by a programmable DC feed network referenced to RSN (receive summing node). Its receive path provides 500× transimpedance gain, while transmit path delivers unity-gain metallic voltage via VTX output with 3 Ω output impedance.
It integrates configurable detector logic (via C3–C1/E1 inputs), open-collector relay drivers with zener clamping to BGND, and chopper-stabilized switching regulator control (CHCLK at 256 kHz typical, CHS, L, VREG, QBAT). The device supports both regulated and unregulated battery operation and includes dedicated pins for anti-saturation (CAS), high-pass filtering (HPA/HPB), and ground-key noise suppression (GKFIL).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Battery Range | –19 V to –58 V: Enables direct connection to telecom central office battery without external regulation. |
| Receive Current Gain | 500×: Converts loop current into precise voltage at RSN for accurate off-hook/loop detection and signal processing. |
| VTX Output Impedance | 3 Ω: Ensures stable two-wire termination and minimizes echo in hybrid circuits. |
| Loop Current (Active) | 37.0 mA @ –48 V, 600 Ω RL: Meets GR-909 and ITU-T K.20 surge immunity requirements for long-loop operation. |
| Switching Regulator Clock | 256 kHz (typ): Synchronizes chopper-stabilized regulation for low-noise, low-dissipation power conversion. |
| Ground-Key Threshold | 1.0–10.0 kΩ resistance range: Supports reliable ground-start line signaling across varying battery voltages and line conditions. |
| Idle Channel Noise | +7 dBmc (C-message weighted, 0°C to +70°C): Complies with Telcordia GR-303 noise limits for voice-grade lines. |
Pinout & Package
LE7942B-1DJC is housed in a 32-pin PLCC (Plastic Leaded Chip Carrier) package with thermal pad (TP) tied internally to QBAT. The package meets RoHS Directive 2002/95/EC (green package), features matte-tin lead finish, and supports lead-free reflow up to 245°C.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A(TIP) | Output | Power amplifier output driving TIP line; supports –70 V continuous swing relative to BGND. |
| B(RING) | Output | Power amplifier output driving RING line; enables polarity reversal and ground-key detection. |
| RSN | Input | Receive summing node: metallic current = 500 × current injected here; reference point for feed, gain, and impedance networks. |
| VTX | Output | Unity-gain transmit audio output; sources two-wire input impedance programming network; 3 Ω output impedance. |
| GKFIL | Capacitor | External ground-key noise filter connection; requires ≥3300 pF capacitor to AGND/DGND for reliable detection. |
| DET | Output | Open-collector switchhook/ground-key/ring-trip detector output with internal 15 kΩ pull-up; logic state selected by C3–C1/E1. |
| RINGOUT / TESTOUT | Output | Open-collector relay drivers with emitter tied to BGND and internal zener clamp (6–7.2 V); drive external relays directly. |
| L | Output | Switching regulator power transistor node; carries high di/dt pulses up to 60 V; requires short, low-inductance layout. |
| QBAT | Battery | Quiet battery supply for signal processing circuits; internally connected to TP thermal pad for enhanced heat dissipation. |
| AGND/DGND | Gnd | Common analog/digital ground reference; must be star-connected to minimize noise coupling between signal and power domains. |
Key Features
| Feature | Design Value |
|---|---|
| Programmable Constant-Current Feed | Loop current set via RDC1/RDC2 network on RDC pin; supports active/OHT states with ±20% threshold tolerance. |
| On-Chip Switching Regulator Support | Reduces power dissipation by >50% vs. linear regulation; enables efficient –48 V operation with L, CHCLK, CHS, VREG, QBAT pins. |
| Dual Detector Logic Selection | E1 pin selects between ground-key (E1=1) and off-hook/ring-trip (E1=0); C3–C1 decode eight distinct line states including Tip Open and Polarity Reversal. |
| Integrated Relay Drivers | RINGOUT and TESTOUT provide 60 mA sink capability with zener clamping; eliminate need for external driver transistors. |
| Low Standby Power | On-hook open-circuit power dissipation as low as 30 mW @ –24 V (no switching regulator); critical for energy-efficient line cards. |
Applications
| Central Office Line Card | Enterprise PBX Interface |
|---|---|
|
Use Scenario: High-density line card in Class 5 central office switch handling 32+ analog subscriber lines per board. IC Role / Device Role / Timing Role: Primary SLIC providing battery feed, loop supervision, ringing, and hybrid interface for each line. Use Value: Programmable feed and ground-key detection enable compliance with regional telco specifications (e.g., FCC Part 68, ETSI EN 300 386) without hardware changes. |
Use Scenario: Modular analog port module in enterprise PBX supporting hot-swappable line cards with mixed loop lengths. IC Role / Device Role / Timing Role: Line interface IC managing tip/ring voltage, polarity reversal, and relay-controlled test access. Use Value: On-chip switching regulator reduces thermal load and eliminates discrete DC/DC converters, lowering BOM cost and board area. |
| Key Telephone System (KTS) | VoIP Gateway Analog FXS Port |
|
Use Scenario: Feature-rich KTS supporting ground-start trunks, call waiting, and distinctive ring detection. IC Role / Device Role / Timing Role: Subscriber line controller implementing ground-key detection, ring-trip sensing, and test relay actuation. Use Value: Dedicated GKFIL pin and programmable loop-detect threshold ensure robust operation on legacy ground-start lines with variable leakage. |
Use Scenario: Analog telephony adapter (ATA) converting VoIP packets to POTS signals for residential/fax use. IC Role / Device Role / Timing Role: FXS line driver delivering compliant battery feed, on-hook transmission, and longitudinal balance. Use Value: 52 dB longitudinal balance (0–1 kHz) and –64 dB THD meet ITU-T G.117/G.712 for carrier-grade voice quality. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar subscriber line interface applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LE7942BDJC | No performance grading suffix; standard specification grade (vs. –1 grade of LE7942B-1DJC). | Same pinout and functionality; suitable where extended temp range or tighter parametric tolerances are not required. | Select LE7942BDJC for cost-sensitive designs meeting commercial-grade specs without need for –1 grading. |
| LE7942B-2DJC | –2 performance grade: tighter min/max bounds on loop current, gain tracking, and noise vs. –1 grade. | Targeted at industrial-temperature (–40°C to +85°C) deployments and higher-reliability line cards. | Choose LE7942B-2DJC when operating beyond 70°C ambient or requiring enhanced parametric consistency across voltage/temperature. |
Compared with LE7942BDJC and LE7942B-2DJC, the LE7942B-1DJC offers verified performance grading for commercial-temperature line cards-balancing tighter specifications than standard grade while avoiding the cost premium of industrial-grade –2 variants.
Availability
LE7942B-1DJC is available at Aetrix Electronics and suitable for central office line cards, enterprise PBX interfaces, key telephone systems, and VoIP gateway FXS ports requiring stable component supply and long-term lifecycle support.
Supply support for LE7942B-1DJC includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Zarlink Semiconductor (acquired Legerity's SLIC portfolio in August 2007) is a fabless semiconductor company specializing in communications ICs for voice, timing, and broadband infrastructure.
The LE7942B-1DJC belongs to the VE580 Series SLIC family, engineered specifically for high-reliability analog telephony line interface in PBX, KTS, and carrier-grade access equipment.
FAQ
What is the operating temperature range for the LE7942B-1DJC?
The LE7942B-1DJC is specified for commercial temperature operation from 0°C to +70°C. This grade supports deployment in climate-controlled environments such as central office switches and enterprise PBX cabinets. The –1 suffix denotes performance grading over this range, with tighter limits on parameters like loop current accuracy and gain tracking compared to the standard LE7942BDJC variant.
Does the LE7942B-1DJC require an external switching regulator?
No-the LE7942B-1DJC can operate with or without the on-chip switching regulator. When used without it (e.g., at –24 V battery), pins L, CHS, and VREG connect to VBAT, and CHCLK connects to AGND/DGND. With the regulator enabled (e.g., at –48 V), the device uses CHCLK (256 kHz), CHS, L, VREG, and QBAT to achieve lower power dissipation and improved thermal performance.
How does ground-key detection work on the LE7942B-1DJC?
Ground-key detection on the LE7942B-1DJC is enabled by setting E1 = logic high, which routes the ground-key detector output to the DET pin. Detection relies on measuring resistance between B(RING) and ground; thresholds range from 1.0 kΩ to 10.0 kΩ depending on battery voltage. A 3300 pF capacitor on GKFIL suppresses noise to ensure reliable operation in electrically noisy environments.
What are the key differences between LE7942B-1DJC and LE7942B-2DJC?
The LE7942B-2DJC is the industrial-grade variant rated for –40°C to +85°C operation and features tighter parametric tolerances-especially on loop current, idle channel noise, and gain tracking-compared to the commercial-grade LE7942B-1DJC. Both share identical pinout, package, and core functionality, but LE7942B-2DJC is intended for uncontrolled-temperature deployments like outside plant cabinets or remote terminals.
Can the LE7942B-1DJC drive standard electromechanical relays directly?
Yes-the LE7942B-1DJC includes two open-collector relay drivers (RINGOUT and TESTOUT), each capable of sinking up to 60 mA with internal zener clamping to BGND (6–7.2 V breakdown). These outputs can directly drive common telecom relays without external transistors, simplifying board design and improving reliability in test and ring-trip functions.
LE7942B-1DJC Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Subscriber Line Interface Concept (SLIC)
- Interface:
- 2-Wire
- Number of Circuits:
- 1
- Voltage - Supply:
- 4.75V ~ 5.25V
- Current - Supply:
- -
- Power (Watts):
- -
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 32-PLCC (11.43x13.97)
LE7942B-1DJC FAQ
1.How can I place an order for LE7942B-1DJC through Aetrix?
Please submit a Request for Quotation (RFQ) for LE7942B-1DJC on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LE7942B-1DJC reliable?
The price and inventory of LE7942B-1DJC are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LE7942B-1DJC is usually 5 days.
3.What payment methods are accepted for LE7942B-1DJC?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LE7942B-1DJC transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LE7942B-1DJC?
LE7942B-1DJC orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LE7942B-1DJC order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LE7942B-1DJC?
For technical support, including LE7942B-1DJC datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LE7942B-1DJC requirements.
6.How does Aetrix verify that LE7942B-1DJC is sourced from the original manufacturer or authorized distributors?
All LE7942B-1DJC products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LE7942B-1DJC meets industry standards.
7.What is the process for return or replacement of LE7942B-1DJC?
All LE7942B-1DJC units undergo pre-shipment inspection (PSI). If there is an issue with LE7942B-1DJC, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LE7942B-1DJC part is unused and in its original packaging.
Return procedure for LE7942B-1DJC:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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