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Microchip Technology LE7920-2DJCT
- Part No.:
- LE7920-2DJCT
- Manufacturer:
- Microchip Technology
- Category:
- Telecom
- Package:
- 32-LCC (J-Lead)
- Datasheet:
-
LE7920-2DJCT.pdf
- Description:
- IC TELECOM INTERFACE 32PLCC
- Quantity:
- Payment:
- Shipping:
Inventory:2,649
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Product details
Overview
LE7920-2DJCT from Zarlink Semiconductor is a Subscriber Line Interface Circuit (SLIC) designed for POTS line interface cards in telephony systems. It delivers active, ringing, standby, and disconnect control states; supports –19 V to –58 V battery operation; provides programmable constant-current feed and loop-detect threshold; and integrates four on-chip relay drivers-including one dedicated ringing driver-in a 32-pin PLCC package for low-cost, high-performance analog line card designs.
For engineers reviewing the LE7920-2DJCT datasheet, LE7920-2DJCT pinout, LE7920-2DJCT application, or LE7920-2DJCT equivalent, this page delivers verified technical context, exact pin functions, thermal management implementation details, longitudinal balance performance (63 dB), and real-world SLIC design constraints including DC feed programming, on-hook transmission capability, and relay driver open-collector output behavior.
Technical Context
The LE7920-2DJCT implements full two-wire metallic interface functionality using a current gain of 500 at the RSN node, enabling precise DC feed current control via external RDC network and programmable impedance synthesis via VTX–RSN ZT network. Its dual-path signal path supports simultaneous transmit audio (VTX, 0.5× gain) and receive summing (RSN), with independent high-pass filtering on A(TIP) and B(RING) through HPA/HPB pins.
Control logic uses TTL-compatible C2/C1 inputs to select among four operational states-Active, Ringing, Standby, Disconnect-with corresponding DET output behavior and relay driver activation via D1–D3. Thermal Management (TMG) offloads power by connecting an external resistor between TMG and VBAT, reducing junction temperature during high-current Active and Disconnect states.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Battery voltage range | –19 V to –58 V: Enables interoperability across global POTS central office battery supplies without external regulation. |
| Longitudinal balance (L-T) | 63 dB (0°C to +70°C): Meets stringent Bellcore GR-357-CORE requirements for noise immunity in metallic line interfaces. |
| Current gain (RSN) | 500: Defines precise scaling between RSN input current and metallic loop current, critical for accurate feed programming. |
| Standby power dissipation | 35 mW: Minimizes heat generation in idle line cards, supporting high-density chassis deployment. |
| Relay driver outputs | 4 open-collector drivers (RINGOUT, RYOUT1–3), each rated for 50 mA sink: Directly drives electromechanical relays without external transistors. |
| On-hook transmission | Supported via VTX output: Allows monitoring of line status and signaling (e.g., caller ID) while maintaining disconnect state. |
| Thermal Management (TMG) | External RTMG resistor connection: Offloads up to ~300 mW from die during Active/Disconnect, extending reliability at high ambient temperatures. |
Pinout & Package
LE7920-2DJCT is housed in a 32-pin Plastic Leaded Chip Carrier (PLCC) package per JEDEC MS-016, with gull-wing leads, body size 12.3 × 15.0 mm, and pin 1 orientation marked. The package is RoHS-compliant (green, matte-tin plating), compatible with lead-free reflow profiles (peak ≤245°C).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| A(TIP) | Output | Power amplifier output driving telephone line TIP conductor; handles –70 V transient surges and ±150 mA current. |
| B(RING) | Output | Power amplifier output driving telephone line RING conductor; matched to A(TIP) for balanced metallic interface. |
| RSN | Input | Receive summing node: Metallic current = 500 × IRSN; anchor point for DC feed, impedance, and gain networks. |
| VTX | Output | Transmit audio output (0.5× metallic voltage); sources 2-wire AC impedance network and enables on-hook signaling. |
| RDC | Resistor | DC feed programming node: External RDC1/RDC2 network sets constant-current loop feed level (e.g., 20–30 mA). |
| TMG | Thermal Management | Connection point for external RTMG resistor to VBAT; diverts power from die to reduce junction temperature. |
| RYOUT1–3, RINGOUT | Output | Open-collector relay drivers (emitter tied to BGND); sink up to 50 mA each for direct relay coil control. |
| D1–D3 | Input | TTL-compatible relay control inputs: Logic Low activates corresponding RYOUTx driver (D1→RYOUT1, etc.). |
| C2/C1 | Input | State selection bits (C2=MSB): Encode Disconnect (00), Ringing (01), Active (10), Standby (11) control modes. |
| DET | Output | Open-collector switchhook detector output with internal 15 kΩ pull-up; asserts Low on loop or ring-trip detection. |
Key Features
| Feature | Design Value |
|---|---|
| No –5 V supply required | Operates from single +5 V (VCC) and negative battery (VBAT) rails-eliminates need for auxiliary negative regulator and reduces BOM cost. |
| Programmable loop-detect threshold | Set via external RD resistor (e.g., 35.4 kΩ yields 11.5–17.3 mA on-threshold); enables precise off-hook detection across varying loop lengths. |
| Two-wire impedance set by single external network | ZT network between VTX and RSN synthesizes 600 Ω (or other target) AC impedance without discrete transformers or complex matching. |
| On-chip thermal management (TMG) | RTMG resistor diverts power from die during high-current states-reduces junction temperature rise by >20°C vs. no TMG, improving long-term reliability. |
| Four integrated relay drivers | Includes dedicated RINGOUT plus three general-purpose RYOUTx outputs-enables full line card relay control (ringing, tip/ring reversal, test access) without external drivers. |
Applications
| Central Office Line Card | Digital Loop Carrier (DLC) |
|---|---|
|
Use Scenario: High-density line interface card in Class 5 central office switching systems handling 32–96 lines per board. IC Role / Device Role / Timing Role: Primary SLIC providing battery feed, supervision, ringing, and hybrid interface for analog subscriber lines. Use Value: 63 dB longitudinal balance ensures compliance with GR-357-CORE noise limits; low 35 mW standby power enables >100-line density per 1U chassis. |
Use Scenario: Remote terminal unit in digital loop carrier systems serving rural or distributed subscriber populations. IC Role / Device Role / Timing Role: Line interface IC managing local battery backup, loop supervision, and ringing under variable temperature (-40°C to +85°C). Use Value: Wide –19 V to –58 V battery range accommodates aging CO batteries; TMG support maintains reliability in uncooled outdoor cabinets. |
| VoIP Gateway Analog FXS Port | Emergency Call System Interface |
|
Use Scenario: Analog telephone adapter (ATA) or enterprise VoIP gateway providing FXS ports for legacy phone connectivity. IC Role / Device Role / Timing Role: SLIC implementing POTS line emulation including on-hook transmission for caller ID and battery feed for ringer. Use Value: VTX output enables on-hook signaling without breaking disconnect state; programmable ring-trip threshold prevents false alarms on noisy lines. |
Use Scenario: Life-safety system (e.g., fire alarm panel, elevator phone) requiring fail-safe analog line interface with guaranteed ring detection. IC Role / Device Role / Timing Role: Supervisory SLIC delivering certified ringing, loop supervision, and relay-controlled line isolation for emergency circuits. Use Value: Dedicated RINGOUT driver ensures reliable ringing under fault conditions; 63 dB L-T balance rejects EMI from adjacent alarm wiring. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar subscriber line interface applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LE7920-1DJCT | 63 dB longitudinal balance replaced with 53 dB; otherwise identical pinout, package, and electrical specs. | Suitable for less demanding environments where GR-357-CORE 63 dB requirement is waived (e.g., non-carrier-grade gateways). | Select LE7920-1DJCT only if system-level longitudinal noise testing confirms 53 dB suffices; no PCB change needed. |
| Si3217x series (e.g., Si32176) | Higher integration (integrated DC-DC, DSP, PCM interface); different pinout; requires external transformer for isolation. | Targets modern VoIP platforms needing integrated power conversion and digital audio interface (PCM/TDM), not pure analog SLIC replacement. | Use Si32176 only when redesigning for digital interface and embedded power; not a drop-in replacement for LE7920-2DJCT. |
Compared with LE7920-1DJCT, the LE7920-2DJCT delivers 10 dB better longitudinal rejection critical for carrier-grade noise immunity; compared with Si32176, it offers simpler analog-only implementation with no firmware dependency but requires external power and timing resources.
Availability
LE7920-2DJCT is available at Aetrix Electronics and suitable for central office line cards, digital loop carrier terminals, VoIP FXS gateways, and emergency call system interfaces requiring stable component supply, long-lifecycle support, and RoHS-compliant green packaging.
Supply support for LE7920-2DJCT 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 was a fabless semiconductor company specializing in voice, timing, and broadband communications ICs, acquired by Microsemi in 2011 and later integrated into Microchip Technology.
The LE7920-2DJCT belongs to Zarlink's VE580 Series SLIC product line, engineered specifically for cost-sensitive, high-reliability POTS line interface applications in carrier and enterprise telephony infrastructure.
FAQ
What is the function of the TMG pin on the LE7920-2DJCT?
The TMG pin on the LE7920-2DJCT connects to an external resistor (RTMG) between TMG and VBAT to implement on-chip thermal management. During Active and Disconnect states, this resistor diverts power away from the die, reducing junction temperature rise by up to 25°C. For LE7920-2DJCT operating at –48 V battery and 25 mA loop current, RTMG ≥ 2350 Ω is recommended per the thermal equations in the datasheet.
How does the LE7920-2DJCT achieve 63 dB longitudinal balance?
The LE7920-2DJCT achieves 63 dB longitudinal balance (L-T) through precision-matched internal circuitry in its A(TIP)/B(RING) power amplifiers and symmetric layout referenced to BGND and AGND/DGND. This specification is guaranteed over 0°C to +70°C for the –2 performance grade variant and validated per Bellcore GR-357-CORE test methods. The LE7920-2DJCT's balance is measured differentially between VTX and VL in Test Circuit C, not inferred from generic SLIC architecture.
Can the LE7920-2DJCT drive a mechanical ringing relay directly?
Yes, the LE7920-2DJCT can drive a mechanical ringing relay directly using its RINGOUT pin, which is an open-collector output rated for 50 mA sink current with emitter tied to BGND. When D1 is held Low and C2/C1 = 01 (Ringing state), RINGOUT activates. Designers must ensure relay coil voltage drop (typically 3–6 V) and current (≤50 mA) match the VBAT rail and driver capability-no external transistor is required for standard 48 V ringing relays.
What is the purpose of the RSN pin on the LE7920-2DJCT?
The RSN (Receive Summing Node) pin on the LE7920-2DJCT serves as the reference node for all analog signal paths: metallic loop current equals 500 × current injected into RSN; DC feed resistance (RDC), two-wire AC impedance (ZT), and receive gain (ZRX) networks all connect here. It is not a voltage output-it is a low-impedance current-summing point (10–20 Ω) that enables precise, externally programmable control of feed, impedance, and gain without internal op-amps or DACs.
Does the LE7920-2DJCT support on-hook transmission, and how is it implemented?
Yes, the LE7920-2DJCT supports on-hook transmission via its VTX output, which provides a 0.5× gain version of the A(TIP)/B(RING) metallic voltage and remains active in Disconnect and Standby states. This allows transmission of caller ID FSK signals or supervisory tones while the line is on-hook. Implementation requires connecting VTX to the system codec or modem input and ensuring the external 2-wire impedance network (ZT) is properly terminated to maintain return loss.
LE7920-2DJCT Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 32-LCC (J-Lead)
- Packaging:
- Tape & Reel (TR)
- 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)
LE7920-2DJCT FAQ
1.How can I place an order for LE7920-2DJCT through Aetrix?
Please submit a Request for Quotation (RFQ) for LE7920-2DJCT 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 LE7920-2DJCT reliable?
The price and inventory of LE7920-2DJCT are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LE7920-2DJCT is usually 5 days.
3.What payment methods are accepted for LE7920-2DJCT?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LE7920-2DJCT transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LE7920-2DJCT?
LE7920-2DJCT orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LE7920-2DJCT 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 LE7920-2DJCT?
For technical support, including LE7920-2DJCT datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LE7920-2DJCT requirements.
6.How does Aetrix verify that LE7920-2DJCT is sourced from the original manufacturer or authorized distributors?
All LE7920-2DJCT 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 LE7920-2DJCT meets industry standards.
7.What is the process for return or replacement of LE7920-2DJCT?
All LE7920-2DJCT units undergo pre-shipment inspection (PSI). If there is an issue with LE7920-2DJCT, 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 LE7920-2DJCT part is unused and in its original packaging.
Return procedure for LE7920-2DJCT:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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