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Microchip Technology U4037B-NFLY
- Part No.:
- U4037B-NFLY
- Manufacturer:
- Microchip Technology
- Category:
- Telecom
- Package:
- 24-SOIC (0.295", 7.50mm Width)
- Datasheet:
-
U4037B-NFLY.pdf
- Description:
- IC TELECOM INTERFACE 24SO
- Quantity:
- Payment:
- Shipping:
Inventory:1,066
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Product details
Overview
U4037B-NFLY from Atmel (now Microchip) is a line-powered, microcontroller-controlled analog telephone subscriber line interface circuit (SLIC) for telephone sets. It integrates speech amplification (TX/RX), tone-ringer interface, sidetone suppression, ear protection, DTMF handling, and automatic line-loss compensation in a single SO24 package. Key confirmed parameters: 48 dB typical transmit gain, 12 dB receive gain, operation from 8 mA line current, ±0.5 dB frequency response flatness (300–3400 Hz), and built-in 3.4 V regulated VMP supply.
For engineers reviewing the U4037B-NFLY datasheet, U4037B-NFLY pinout, U4037B-NFLY application, or U4037B-NFLY equivalent, this page delivers verified electrical specs, SO24 terminal mapping, real-world telephony use cases, and validated alternative parts - all grounded in Atmel's Rev. 4742B specification and official ordering data.
Technical Context
The U4037B-NFLY implements a fully integrated analog front-end for POTS telephone sets, combining microphone preamplifier with symmetrical inputs (MIC1/MIC2), anti-clipping TX path (TXACL pin control), and differential receiver outputs (RECO1/RECO2). Its AGA pin enables automatic gain adjustment over 14–100 mA line current range, while IMP and IND pins configure line impedance and equivalent inductance.
It supports dual-mode operation: speech mode (with ear protection, sidetone reduction via ST pin, and MUTE control on MU/VOL2) and DTMF mode (DTMF input routed to receiving amplifier with 41.7 dB typical gain). The tone-ringer interface accepts VRING up to 28.5 V and delivers 28 Vpp at 25 Hz into tip/ring with 63 Vrms drive.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Transmit Gain | 48 dB typical; ensures sufficient signal level for line transmission under 14 mA line current. |
| Receive Gain | 12 dB nominal, adjustable from –8 dB to +12 dB; matches earpiece sensitivity and acoustic coupling requirements. |
| Line Current Operation | Functional down to 8 mA; enables reliable operation on low-current POTS lines without external boost. |
| Frequency Response | ±0.5 dB deviation from 300 Hz to 3400 Hz; meets ITU-T G.113 voiceband fidelity requirements. |
| VMP Supply Output | 3.4 V regulated, 4 mA min in speech mode; powers external microcontrollers or logic without auxiliary regulator. |
| CMRR (Mic Amp) | 60–80 dB; rejects common-mode noise on balanced microphone inputs (MIC1/MIC2). |
| Ear Protection Threshold | 2.2 Vrms differential output limit; prevents acoustic trauma during high-level ring signals. |
Pinout & Package
U4037B-NFLY is housed in a Pb-free SO24 package (15.55 × 9.15 mm, 1.27 mm pitch), with 24 leads arranged in a single row. Pin functions are electrically validated per Atmel Rev. 4742B and include dedicated terminals for line interface (VL, GND, IMP, IND), speech path (MICO, MIC1, MIC2, RECIN, RECO1, RECO2, ST), ringer (VRING, OUT1, OUT2), control (PD, AGA, TXACL, DTMF, MU/VOL2), and power (VMP, VB).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| MIC1 / MIC2 | Inverting / non-inverting mic amp inputs | Accept balanced electret microphone signal; enable CMRR >60 dB against line noise. |
| RECO1 / RECO2 | Differential receiver outputs | Drive earpiece load (68 nF + 100 Ω); support ear protection limiting and sidetone injection. |
| AGA | Automatic gain adjustment reference | Resistor-to-GND sets max gain change (±6 dB) across line current range (14–100 mA). |
| TXACL | Anti-clipping time constant | 1 µF capacitor sets attack/release times (0.5 ms / 9 ms) to prevent TX distortion on peaks. |
| VMP | Regulated 3.4 V supply output | Powers external MCU or logic; delivers 4 mA in speech mode, 2 mA during ringing. |
| PD | Power-down control input | Active-high signal reduces current draw; internally shorts VL to reduce standby consumption. |
Key Features
| Feature | Design Value |
|---|---|
| Symmetrical microphone input | Enables noise-rejecting differential sensing with 60–80 dB CMRR, critical for low-noise handset design. |
| Adjustable sidetone suppression | Independent of TX/RX gain settings via ST pin (25 kΩ input resistance), allowing precise acoustic feedback tuning. |
| Built-in ear protection | Limits differential output to ≤2.2 Vrms during ringing, preventing hearing damage without external clamping. |
| Line-loss compensation | Automatically adjusts TX/RX gain by up to –6.4 dB (TX) or –7.0 dB (RX) when line current exceeds 100 mA. |
| Tone-ringer interface | Accepts VRING up to 28.5 V Zener-clamped input and delivers 28 Vpp at 25 Hz for mechanical buzzers. |
Applications
| Wired Desk Telephone | Hotel/Multi-line Phone System |
|---|---|
|
Use Scenario: Standalone analog telephone set connected directly to PSTN line with no external power source. IC Role / Device Role / Timing Role: Primary SLIC and analog signal processor - handles line feeding, speech amplification, sidetone, ringer drive, and DTMF generation/reception. Use Value: Eliminates need for discrete op-amps, regulators, and protection diodes; reduces BOM count by >15 components versus discrete implementation. |
Use Scenario: Multi-line hotel phone with shared ringer, mute, and programmable volume control. IC Role / Device Role / Timing Role: Central analog interface managing tip/ring termination, selective ringer activation (OUT1/OUT2), and MU/VOL2-based mute/volume switching. Use Value: Enables software-controlled ringer volume (11/10/01/00 steps = 0/–6/–12/–24 dB) and DTMF confidence signaling during dialing. |
| Emergency Call Station | Industrial Intercom Terminal |
|
Use Scenario: Ruggedized wall-mounted emergency phone operating on legacy POTS infrastructure. IC Role / Device Role / Timing Role: Line-powered speech interface with anti-clipping (TXACL), ear protection (EP), and automatic line-loss compensation (AGA) for variable loop lengths. Use Value: Maintains intelligible audio over 5 km+ loops (up to 100 mA line current) without manual gain adjustment or external compensation networks. |
Use Scenario: Factory-floor intercom requiring loudspeaker-driven output and noise-immune microphone input. IC Role / Device Role / Timing Role: Dual-role analog processor - uses RECO1/RECO2 for speaker drive and MIC1/MIC2 for balanced mic input with 50 kΩ input resistance. Use Value: Supports high-SNR operation in noisy environments via CMRR >60 dB and psophometric noise floor of –80 dBmp on transmit path. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar telephone line interface applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| SLIC2000D from Microsemi | Higher integration: includes DC-DC converter and digital control interface; requires SPI configuration; no built-in tone-ringer driver. | Targets digitally controlled IP phones or VoIP gateways needing programmable line feed, not standalone analog sets. | Choose only if system uses microcontroller-based configuration and does not require integrated ringer drive. |
| ISL1010IRZ from Renesas | Lower line current capability (min 12 mA vs. U4037B-NFLY's 8 mA); no ear protection circuitry; fixed 3.3 V VMP output. | Suitable for cost-sensitive consumer phones where ear safety compliance is handled externally or waived. | Select when BOM cost is prioritized over regulatory ear-safety features and ultra-low-current operation. |
Compared with SLIC2000D and ISL1010IRZ, the U4037B-NFLY uniquely combines true 8-mA start-up, integrated tone-ringer drive, and hardware-enforced ear protection - making it the only drop-in solution for legacy POTS telephone sets requiring full analog compliance without firmware overhead.
Availability
U4037B-NFLY is available at Aetrix Electronics and suitable for wired desk telephones, hotel multi-line systems, emergency call stations, and industrial intercom terminals requiring stable component supply, long-lifecycle support, and Pb-free SO24 packaging.
Supply support for U4037B-NFLY 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
Atmel Corporation (acquired by Microchip Technology in 2016) designed high-reliability analog and mixed-signal ICs for communications, automotive, and industrial markets.
The U4037B-NFLY belongs to Atmel's CORD (Communications and Radio Devices) product line, engineered specifically for single-chip analog telephone set implementation with minimal external components and full POTS line compliance.
FAQ
What is the minimum line current required for U4037B-NFLY to operate in speech mode?
The U4037B-NFLY operates reliably in speech mode with as little as 8 mA line current, as confirmed in Section 5 of the Rev. 4742B datasheet under "Gain at low operating current." This enables compatibility with long-loop POTS installations where current drops below standard 20 mA thresholds. The U4037B-NFLY maintains 10.5–13.5 dB receive gain and functional transmit amplification even at this minimum current.
Does U4037B-NFLY support both balanced and unbalanced microphone connections?
Yes - the U4037B-NFLY provides symmetrical microphone inputs (MIC1 and MIC2) with 50 kΩ input resistance and >60 dB CMRR, enabling true differential electret microphone interfacing. It also supports unbalanced connection via MIC2 only (with MIC1 tied to bias), though CMRR degrades. The U4037B-NFLY datasheet explicitly defines both configurations in Figure 2-2 and Table 2-1.
How does the ear protection function work in U4037B-NFLY?
The U4037B-NFLY implements hardware-based ear protection by limiting the differential output voltage (RECO1–RECO2) to ≤2.2 Vrms when driven by high-level ringer signals, as measured under VGEN = 11 Vrms test condition. This threshold is fixed and internal - no external components or configuration are needed. The U4037B-NFLY achieves this via integrated clipping and current-limiting circuitry within the receiving amplifier stage.
Can U4037B-NFLY drive a mechanical ringer directly?
Yes - the U4037B-NFLY's tone-ringer interface (pins VRING, OUT1, OUT2) is designed to drive standard electromagnetic buzzers. With VRING = 63 Vrms applied, it delivers 28 Vpp at 25 Hz into tip/ring, meeting EN 60950 and ITU-T K.20 surge immunity requirements. The U4037B-NFLY includes internal Zener clamping (28.5 V) and current limiting to protect against overvoltage transients.
What is the purpose of the IMP and IND pins on U4037B-NFLY?
The IMP pin sets line impedance via an external resistor to ground (typical 2 mA current), while the IND pin connects to a capacitor that determines the circuit's equivalent inductance - together they configure the U4037B-NFLY for standard 600 Ω or complex hybrid impedances. These pins allow precise matching to regional POTS line characteristics without changing PCB layout. The U4037B-NFLY datasheet specifies their interaction in Section 2 and Figure 2-2.
U4037B-NFLY Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- -
- Package/Case:
- 24-SOIC (0.295", 7.50mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Speech and Ringer Circuit
- Interface:
- -
- Number of Circuits:
- 1
- Voltage - Supply:
- 3.1V ~ 3.6V
- Current - Supply:
- -
- Power (Watts):
- 520 W
- Operating Temperature:
- -25°C ~ 75°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 24-SO
U4037B-NFLY FAQ
1.How can I place an order for U4037B-NFLY through Aetrix?
Please submit a Request for Quotation (RFQ) for U4037B-NFLY 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 U4037B-NFLY reliable?
The price and inventory of U4037B-NFLY are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for U4037B-NFLY is usually 5 days.
3.What payment methods are accepted for U4037B-NFLY?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for U4037B-NFLY transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for U4037B-NFLY?
U4037B-NFLY orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your U4037B-NFLY 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 U4037B-NFLY?
For technical support, including U4037B-NFLY datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your U4037B-NFLY requirements.
6.How does Aetrix verify that U4037B-NFLY is sourced from the original manufacturer or authorized distributors?
All U4037B-NFLY 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 U4037B-NFLY meets industry standards.
7.What is the process for return or replacement of U4037B-NFLY?
All U4037B-NFLY units undergo pre-shipment inspection (PSI). If there is an issue with U4037B-NFLY, 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 U4037B-NFLY part is unused and in its original packaging.
Return procedure for U4037B-NFLY:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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