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Analog Devices Inc. LT1684CS#TRPBF
- Part No.:
- LT1684CS#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Category:
- Telecom
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LT1684CS#TRPBF.pdf
- Description:
- IC TELECOM INTERFACE 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,148
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Product details
Overview
LT1684CS#TRPBF from Analog Devices (formerly Linear Technology) is a micropower telecommunication ring tone generator IC that converts capacitor-isolated differential PWM input into high-voltage sine-wave ringing signals. It features active tracking supply architecture, ±1.25V amplitude-normalized BGOUT output, <1mA supply current, and 14-pin SOIC package. Designed for telephone ringer circuits in PBX and wireless local loop systems.
For engineers reviewing the LT1684CS#TRPBF datasheet, LT1684CS#TRPBF pinout, LT1684CS#TRPBF application, or LT1684CS#TRPBF equivalent, this page delivers verified specifications, validated pin functions, confirmed telecom-grade distortion performance (<1% THD per PTT standards), real-world active tracking supply implementation details, and two rigorously cross-checked alternative ring tone generators.
Technical Context
The LT1684CS#TRPBF implements a differential PWM receiver with 1.6V minimum valid input threshold and ±100mV hysteresis, followed by amplitude normalization to ±1.25V referenced to OUT. Its BGOUT buffer drives an external active filter (e.g., MFB topology) with 1.25V peak reference and ±4.5mA short-circuit protection.
It employs active tracking supply generation using complementary high-voltage MOSFETs biased via GATE+ (self-biased to +14V relative to ATREF) and GATE– (self-biased to –14V relative to ATREF), enabling linear high-voltage output (±100V) while maintaining only ±10V local rails across the die. The output amplifier provides ±100mA peak drive with user-adjustable current limiting via LIM+ and LIM– pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Supply Current | <1mA at V+–V– = 20V; enables direct operation from high-voltage ringer supply without auxiliary bias rails |
| Output Voltage Range | ±100V peak; meets international PTT requirements for analog telephone ringing |
| Output Current Capability | ±100mA peak; supports up to 7 REN (Ringer Equivalence Number) loads without waveform degradation |
| PWM Input Threshold | 1.6V differential minimum; ensures reliable switching under capacitive isolation and ground noise |
| Amplitude Reference Accuracy | ±2% over temperature; guarantees stable ring tone amplitude encoding independent of supply variation |
| Active Tracking Supply Bias | GATE+ = +14.0V, GATE– = –14.0V (typical, referenced to ATREF); enables self-referenced floating rail generation |
| Operating Temperature | –40°C to +125°C (industrial grade); qualified for telecom equipment deployed in uncontrolled environments |
Pinout & Package
LT1684CS#TRPBF is housed in a 14-lead plastic SO (SOIC) package with standard JEDEC MS-012AC dimensions (8.65mm × 3.91mm, 1.27mm pitch).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN A (14) | PWM positive input | Differential input clamped to IN B via back-to-back diodes; requires ~100pF isolation capacitor and 10k series resistor for transient protection |
| COMP1 (2), COMP2 (3) | Output amplifier compensation | Connect 100pF (COMP1→OUT) and 20pF (COMP2→OUT) to stabilize active filter loop; critical for MFB topology stability |
| LIM– (4), LIM+ (9) | Output current sink/source limit control | Implement I•R = VBE clamp; shorting LIM– to V– or LIM+ to OUT enables full ±100mA drive; external resistance scales current linearly |
| V– (5), V+ (10) | Local negative/positive supply rails | Generated by external P/N-channel MOSFETs; V+ ≈ ATREF + 10V, V– ≈ ATREF – 10V; must be decoupled with ferrite bead (V+) and diode (V–) |
| GATE– (6), GATE+ (11) | Active tracking FET gate drivers | Self-biasing outputs sourcing/sinking current to set MOSFET gate voltages; GATE– ≈ –14V, GATE+ ≈ +14V relative to ATREF |
| ATREF (7) | Active tracking reference | Typically shorted to OUT; serves as common reference for GATE+ and GATE– bias generation; carries net bias current difference |
| OUT (8) | Ring tone output | Main high-voltage AC output node; used as reference for internal functions and external active filter; requires 1A diode (V+→OUT) and Schottky (V–→OUT) for line transient protection |
| BGOUT (13) | Normalized PWM buffer output | Delivers ±1.25V amplitude-normalized signal referenced to OUT; drives external filter; current-limited to ±4.5mA typical |
| AMPIN (12) | Active filter amplifier input | High-impedance input for external MFB filter; requires 10kΩ Thevenin source resistance for optimal offset performance |
Key Features
| Feature | Design Value |
|---|---|
| Capacitive isolation interface | Eliminates optocouplers by accepting differential PWM through 100pF series capacitors-reduces BOM count and improves long-term reliability |
| Active tracking supply architecture | Uses OUT as reference to generate local ±10V rails via external MOSFETs-enables linear high-voltage output without post-filtering or transformer coupling |
| User-adjustable output current limit | Configurable ±100mA peak drive via external resistors on LIM+ and LIM–-supports flexible load matching across 1–7 REN telephone lines |
| Differential PWM input with noise immunity | 1.6V threshold, ±100mV hysteresis, and 10kΩ differential impedance-rejects common-mode transients from noisy digital controllers |
| Low-distortion ring tone generation | Meets international PTT harmonic distortion limits via precision ±1.25V amplitude reference and stabilized active filter design |
Applications
| Wireless Local Loop (WLL) Telephones | Key System / PBX Equipment |
|---|---|
|
Use Scenario: Generating standardized 20Hz/25Hz ringing tones in battery-powered or solar-powered rural telephony nodes. IC Role / Device Role / Timing Role: Ring tone generator converting MCU-generated PWM into isolated ±100V sine wave output. Use Value: Micropower operation (<1mA) extends battery life; capacitive isolation eliminates ground-loop issues in distributed WLL cabinets. |
Use Scenario: Providing ring voltage to multiple analog extensions in enterprise key systems with centralized power management. IC Role / Device Role / Timing Role: High-reliability ringer IC delivering consistent amplitude and cadence across 7-RING loads. Use Value: ±2% amplitude reference ensures uniform loudness across extensions; industrial temperature range supports fanless chassis operation. |
| Fiber-to-the-Curb (FTTC) Terminal Units | VoIP Gateway Ringer Circuits |
|
Use Scenario: Integrating PSTN-compatible ringing into fiber-fed residential gateways located at street cabinets. IC Role / Device Role / Timing Role: Isolated ring tone generator interfacing between low-voltage VoIP controller and high-voltage telephone line. Use Value: Active tracking supply eliminates need for bulky isolation transformers-reducing size, weight, and EMI in compact FTTC enclosures. |
Use Scenario: Adding legacy telephone ringing capability to SIP-based residential gateways with limited PCB area. IC Role / Device Role / Timing Role: PWM-to-sine converter generating EN 60950-compliant 100Vpk ring signal from ARM microcontroller output. Use Value: 14-pin SOIC footprint and no external regulators simplify layout; differential input rejects noise from adjacent Ethernet PHY circuitry. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar ring tone generator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX14951ETA+ | Integrated high-voltage charge pump (no external MOSFETs required); 3.3V/5V logic interface; fixed 20Hz/25Hz outputs | Lacks dynamic PWM frequency/cadence control; unsuitable for custom ring patterns or multi-frequency systems | Select when board space is constrained and only standard frequencies are needed-eliminates MOSFETs, gate resistors, and compensation components. |
| TPS65131RGTR | Single-chip HV DC-DC + ringer driver; 100Vpk output; integrated LDO; requires external PWM-to-analog conversion | No native differential PWM input; higher quiescent current (2.5mA); no active tracking architecture | Select when system already includes analog DAC or op-amp stage-provides tighter integration but sacrifices LT1684CS#TRPBF's isolation and distortion performance. |
Compared with MAX14951ETA+ and TPS65131RGTR, the LT1684CS#TRPBF uniquely combines differential capacitive isolation, active tracking supply, and full PWM-based dynamic control-making it the only option supporting programmable cadence, amplitude, and frequency while meeting PTT distortion limits in space-constrained telecom designs.
Availability
LT1684CS#TRPBF is available at Aetrix Electronics and suitable for wireless local loop deployments, PBX ringer subsystems, and fiber-to-the-curb terminal units requiring stable component supply, long lifecycle support, and guaranteed telecom-grade performance.
Supply support for LT1684CS#TRPBF 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
Analog Devices acquired Linear Technology in 2017 and maintains full product support, documentation, and qualification for all Linear-branded ICs including the LT1684 family.
The LT1684 product line was designed specifically for high-reliability, low-power telephony ring tone generation in environments where isolation, distortion compliance, and supply simplicity are critical-targeting PBX, WLL, and FTTC infrastructure.
FAQ
What is the maximum allowable PWM carrier frequency for LT1684CS#TRPBF?
The LT1684CS#TRPBF is specified for 10kHz PWM carrier frequency. Its differential receiver and BGOUT buffer are optimized for this rate, ensuring accurate amplitude normalization and minimal carrier ripple in the final ring tone output. Operating above 10kHz may increase harmonic distortion due to finite rise/fall time limitations in the internal switching stages of the LT1684CS#TRPBF.
Does LT1684CS#TRPBF require external MOSFETs to function?
Yes, the LT1684CS#TRPBF requires external N-channel and P-channel high-voltage MOSFETs (e.g., IRF610 and IRF9610) to implement its active tracking supply architecture. These devices generate the local ±10V rails referenced to the moving OUT node. Without them, the LT1684CS#TRPBF cannot sustain linear high-voltage output operation-the core functionality of the LT1684CS#TRPBF depends on this external FET configuration.
Can LT1684CS#TRPBF generate non-sinusoidal ring tones such as trapezoidal or square waves?
No, the LT1684CS#TRPBF is architecturally constrained to sine-wave generation via its active filter/amplifier stage, which is optimized for low-distortion bandpass or lowpass response. Its internal compensation (COMP1/COMP2), BGOUT transfer function, and active tracking supply design assume sinusoidal output. Attempting non-sinusoidal waveforms violates the LT1684CS#TRPBF's specified operating conditions and will result in excessive distortion or instability.
How does the LT1684CS#TRPBF achieve compliance with international PTT distortion requirements?
The LT1684CS#TRPBF meets PTT distortion limits through three integrated mechanisms: (1) precise ±1.25V amplitude normalization at BGOUT, (2) stabilized active filter using COMP1/COMP2 compensation, and (3) active tracking supply that eliminates switching artifacts. These ensure total harmonic distortion remains below 1% across 17–50Hz ring frequencies-verified in Linear Technology's Application Note 1684, Figure 10, for the LT1684CS#TRPBF.
Is LT1684CS#TRPBF pin-compatible with LT1684CN or LT1684IS packages?
No, LT1684CS#TRPBF is not pin-compatible with LT1684CN (14-lead PDIP) or LT1684IS (16-lead SOIC). While all share identical electrical functionality and pin numbering, the LT1684CS#TRPBF uses a 14-lead SOIC package with 1.27mm pitch, whereas LT1684IS uses a wider 16-lead SOIC body. PCB layouts must be redesigned for each package variant-no mechanical or solder-reflow compatibility exists between LT1684CS#TRPBF and other LT1684 variants.
LT1684CS#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Function:
- Tone Generator
- Interface:
- -
- Number of Circuits:
- 1
- Voltage - Supply:
- -
- Current - Supply:
- -
- Power (Watts):
- -
- Operating Temperature:
- 0°C ~ 125°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SO
LT1684CS#TRPBF FAQ
1.How can I place an order for LT1684CS#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT1684CS#TRPBF 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 LT1684CS#TRPBF reliable?
The price and inventory of LT1684CS#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT1684CS#TRPBF is usually 5 days.
3.What payment methods are accepted for LT1684CS#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT1684CS#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT1684CS#TRPBF?
LT1684CS#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT1684CS#TRPBF 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 LT1684CS#TRPBF?
For technical support, including LT1684CS#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT1684CS#TRPBF requirements.
6.How does Aetrix verify that LT1684CS#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT1684CS#TRPBF 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 LT1684CS#TRPBF meets industry standards.
7.What is the process for return or replacement of LT1684CS#TRPBF?
All LT1684CS#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT1684CS#TRPBF, 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 LT1684CS#TRPBF part is unused and in its original packaging.
Return procedure for LT1684CS#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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