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Analog Devices Inc./Maxim Integrated MAX1856EUB+TG51
- Part No.:
- MAX1856EUB+TG51
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Special Purpose Regulators
- Package:
- -
- Datasheet:
-
MAX1856EUB+TG51.pdf
- Description:
- INTEGRATED CIRCUIT
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Product details
Overview
The MAX1856EUB+TG51 from Maxim Integrated is a wide-input-range, synchronizable current-mode PWM controller for SLIC (Subscriber Line Interface Circuit) power supplies, generating dual negative outputs (e.g., −24V and −72V) or single outputs (e.g., −48V, −5V, −15V, up to −185V), operating from 3V to 28V input, with adjustable 100kHz–500kHz switching frequency and internal soft-start. It targets voice-enabled broadband CPE including VoIP phones, DSL/cable modems, and FTTH equipment.
For engineers reviewing the MAX1856EUB+TG51 datasheet, MAX1856EUB+TG51 pinout, MAX1856EUB+TG51 application, or MAX1856EUB+TG51 equivalent, key selection considerations include its flyback topology with idle mode efficiency optimization, −24V/−72V dual-output capability, 10-pin µMAX package, low audio-band noise on talk battery, and external clock synchronization support for EMI-sensitive designs.
Technical Context
The MAX1856EUB+TG51 implements a current-mode PWM control architecture with direct-summing comparator eliminating traditional error amplifier phase shift, enabling cycle-by-cycle output voltage regulation via peak inductor current control. Its inverting flyback configuration supports high negative voltage generation while maintaining stable cross-regulation between dual outputs.
It integrates an internal 5V LDO regulator (2.7V–5.5V output, 12mA max), reference (1.25V ±25mV), and logic-level shutdown/sync input (VIH = 2.0V, VIL = 0.45V). Idle Mode™ reduces quiescent current at light loads, with switchover threshold set at 15mV CS voltage (15% of full-scale 100mV current limit).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 28V - enables use with unregulated wall adapters and cost-sensitive DC supplies in xDSL, cable modems, and set-top boxes. |
| Output Voltage Range | Adjustable negative outputs up to −185V - supports MEMS bias, DSL CO line drivers, and SLIC ringer/off-hook supplies via external resistor divider. |
| Switching Frequency | 100kHz to 500kHz (set by ROSC) or synchronized externally - allows EMI optimization and transformer size reduction. |
| Current Limit Threshold | 85mV to 115mV at CS pin - provides accurate overcurrent protection with external sense resistor, independent of temperature and supply variation. |
| LDO Output | 5.00V ±0.5V (at 400Ω load) - powers internal circuitry and EXT gate driver; dropout ≤300mV at 12mA ensures operation down to VCC = 3V. |
| Reference Voltage | 1.250V ±25mV (REF to FB) - enables precise output voltage setting with <0.013%/mV load regulation on feedback path. |
| Shutdown Current | 3.5µA to 6µA at VCC = 28V - minimizes system standby power in life-line support applications. |
Pinout & Package
The MAX1856EUB+TG51 is housed in a 10-pin µMAX package (3mm × 3mm, 0.5mm pitch), thermally enhanced with exposed PGND pad for improved power dissipation in compact CPE designs.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| LDO (Pin 1) | Internal 5V LDO output | Powers all internal blocks and EXT gate driver; requires ≥1µF ceramic bypass to GND for stability. |
| FREQ (Pin 2) | Oscillator frequency set input | Connects to GND via ROSC (100kΩ–500kΩ) to set fOSC = 50MΩ-kHz / ROSC; required even when SYNC/SHDN is clocked. |
| GND (Pin 3) | Analog ground reference | Provides low-noise return for REF, FB, and CS; must be separated from PGND except at single-point Kelvin sense location. |
| REF (Pin 4) | 1.25V precision reference output | Sources up to 400µA; used with FB to set output voltage; requires 2.2µF ceramic bypass for regulation integrity. |
| FB (Pin 5) | Feedback input (0V threshold) | Accepts resistive divider from output(s); zero-volt threshold simplifies dual-output feedback design with split resistor networks. |
| CS (Pin 6) | Positive current-sense input | Monitors voltage across external RCS; 85–115mV threshold enables accurate peak-current limiting and overcurrent protection. |
| PGND (Pin 7) | Power ground | High-current return for EXT driver and MOSFET source; connects to GND only at Kelvin sense point near RCS. |
| EXT (Pin 8) | External MOSFET gate driver | Swings rail-to-rail between LDO and PGND; drives N-channel FET; capable of >1A peak sink/source current. |
| VCC (Pin 9) | Main supply input | Accepts 3V–28V unregulated input; powers LDO input; requires 1µF ceramic bypass to PGND. |
| SYNC/SHDN (Pin 10) | Shutdown control & sync input | Logic-low = shutdown (3.5–6µA ICC); logic-high = free-running at ROSC; rising edge = sync mode (100–500kHz range). |
Key Features
| Feature | Design Value |
|---|---|
| Idle Mode™ Control | Reduces operating current at light loads by pulsing only as needed-enables >80% efficiency at 10% load in −48V/200mA applications. |
| Internal Soft-Start | Digital soft-start (no external capacitor) ramps peak current in 5 steps over 1024 cycles and holds fOSC at 1/3 rate until VOUT reaches 20%-prevents inrush stress on input capacitors. |
| Current-Mode PWM | Direct-summing comparator eliminates error amplifier phase lag-provides inherent cycle-by-cycle regulation and stable cross-regulation across dual outputs without external compensation. |
| Low Audio-Band Noise | Optimized switching behavior and internal filtering minimize noise in 300Hz–3.4kHz band-ensures clean talk battery for voice-grade SLIC performance. |
| Ring Trip Transient Handling | Sturdy output stage and fast transient response maintain regulation during abrupt ring trip events-critical for reliable ringer battery operation in VoIP and CPE. |
Applications
| VoIP Ringer and Off-Hook Supply | DSL CO Line Driver Supply |
|---|---|
Use Scenario: Generating −72V ringer and −24V off-hook voltages for multi-line VoIP phones and residential gateways using standard off-the-shelf transformers. IC Role / Device Role / Timing Role: Primary PWM controller in inverting flyback topology; regulates dual negative outputs with cross-regulation <±1.5% across 0–400mA load range. Use Value: Eliminates need for custom magnetics-reduces BOM cost and time-to-market while meeting GR-909 ring trip and talk battery noise requirements. | Use Scenario: Providing −5V and −15V bias supplies for central office DSL line drivers in broadband access systems. IC Role / Device Role / Timing Role: Dual-output negative voltage generator with independent feedback paths; supports simultaneous −5V/−15V at up to 320mA/150mA per rail. Use Value: Enables compact, high-efficiency power solution compliant with ITU-T G.992.1 (G.dmt) line driver voltage tolerances (±1%) and ripple limits (<10mVpp). |
| MEMS Bias Supply | FTTH Terminal Power |
Use Scenario: Delivering up to −185V bias voltage for MEMS optical switches and tunable filters in metro/core optical networks. IC Role / Device Role / Timing Role: High-voltage negative output controller; uses transformer turns ratio and feedback scaling to achieve >150V output with <0.5% line/load regulation. Use Value: Replaces discrete charge-pump or Cockcroft-Walton multipliers-improves reliability, reduces footprint, and enables programmable voltage adjustment via resistor network. | Use Scenario: Powering GPON/EPON ONUs with −48V backup supply and auxiliary −5V logic rails in fiber-to-the-home terminals. IC Role / Device Role / Timing Role: Single-output −48V SLIC supply with 200mA capability and 85% peak efficiency at 12V input; supports life-line operation during AC failure. Use Value: Meets Telcordia GR-1089 Class A EMI requirements when synchronized to system clock-avoids interference with PON burst-mode upstream transmission. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar SLIC power supply applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1857EUB+ | Same pinout and function but rated for −40°C to +125°C industrial temp range; identical electrical specs and package. | Required for extended-temperature CPE deployed in outdoor enclosures or uncontrolled environments. | Select MAX1857EUB+ when ambient operating temperature exceeds +85°C; otherwise MAX1856EUB+TG51 is optimal for commercial CPE. |
| LM5020MMX/NOPB | Fixed-frequency current-mode PWM controller (no LDO, no REF, no Idle Mode); requires external 5V bias and separate reference; 100kHz–1MHz range. | Used in non-SLIC isolated flyback designs where dual negative outputs and low audio-band noise are not required. | Choose LM5020MMX/NOPB only if redesigning for higher frequency (>500kHz), lower cost, and no need for integrated LDO or SLIC-specific features like ring trip handling. |
Compared with MAX1857EUB+, the MAX1856EUB+TG51 offers identical functionality at lower cost for commercial-temperature CPE, while LM5020MMX/NOPB lacks integrated regulation and SLIC-optimized features-making it suitable only for generic isolated flyback, not voice-grade negative supply generation.
Availability
MAX1856EUB+TG51 is available at Aetrix Electronics and suitable for VoIP gateways, DSL modems, and FTTH ONUs requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.
Supply support for MAX1856EUB+TG51 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
Maxim Integrated (now part of Analog Devices) is a semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for communications, computing, and industrial applications.
The MAX1856EUB+TG51 belongs to Maxim's SLIC power supply controller product line, designed specifically to replace discrete solutions in voice-enabled broadband CPE with integrated, transformer-flexible, low-noise negative voltage generation.
FAQ
What is the maximum negative output voltage achievable with the MAX1856EUB+TG51?
The MAX1856EUB+TG51 supports negative output voltages up to −185V, as confirmed in the General Description and Applications sections. This capability is achieved using standard off-the-shelf transformers and appropriate feedback resistor scaling-enabling use in MEMS bias supplies and other high-voltage negative rail applications. The MAX1856EUB+TG51 achieves this through its inverting flyback topology and precise 1.25V reference, not by internal voltage multiplication.
Does the MAX1856EUB+TG51 require external loop compensation components?
No, the MAX1856EUB+TG51 does not require external loop compensation. Its current-mode PWM architecture with direct-summing comparator eliminates the need for an external error amplifier and associated compensation network. Stability is inherently maintained across load and line variations, as verified in the Detailed Description section and functional diagram (Figure 2). This simplifies design and reduces BOM count for the MAX1856EUB+TG51.
How does the MAX1856EUB+TG51 handle ring trip transients in SLIC applications?
The MAX1856EUB+TG51 handles ring trip transients through a combination of robust output stage design, fast transient response (<1ms recovery per Typical Operating Characteristics), and optimized current-limit threshold (85–115mV). Its ability to sustain high peak currents and maintain regulation under abrupt load changes-demonstrated in the "RINGER TO TALK-BATTERY CROSSTALK" and "LOAD TRANSIENT" waveforms-is integral to SLIC compliance. This behavior is intrinsic to the MAX1856EUB+TG51's architecture.
Can the MAX1856EUB+TG51 generate both −24V and −72V simultaneously?
Yes, the MAX1856EUB+TG51 is explicitly designed for dual-output operation, with the Typical Operating Circuit (Figure 1) demonstrating simultaneous −24V (400mA max) and −72V (100mA max) generation. Cross-regulation is maintained within ±1.5% across load conditions, as shown in Figures toc02 and toc05. This dual-output capability is a core specification of the MAX1856EUB+TG51 and validated across temperature and input voltage ranges.
What is the purpose of the EXT pin on the MAX1856EUB+TG51?
Pin 8 (EXT) on the MAX1856EUB+TG51 is the external N-channel MOSFET gate driver output, swinging rail-to-rail between LDO (≈5V) and PGND. It delivers >1A peak current to drive the primary-side switch in the flyback converter. Its design enables efficient, low-loss switching with minimal external components-confirmed by the EXT sink/source current (1A) and on-resistance (2–5Ω) specifications in the Electrical Characteristics table for the MAX1856EUB+TG51.
MAX1856EUB+TG51 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- -
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Applications:
- -
- Voltage - Input:
- -
- Number of Outputs:
- -
- Voltage - Output:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
MAX1856EUB+TG51 FAQ
1.How can I place an order for MAX1856EUB+TG51 through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1856EUB+TG51 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 MAX1856EUB+TG51 reliable?
The price and inventory of MAX1856EUB+TG51 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1856EUB+TG51 is usually 5 days.
3.What payment methods are accepted for MAX1856EUB+TG51?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1856EUB+TG51 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1856EUB+TG51?
MAX1856EUB+TG51 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1856EUB+TG51 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 MAX1856EUB+TG51?
For technical support, including MAX1856EUB+TG51 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1856EUB+TG51 requirements.
6.How does Aetrix verify that MAX1856EUB+TG51 is sourced from the original manufacturer or authorized distributors?
All MAX1856EUB+TG51 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 MAX1856EUB+TG51 meets industry standards.
7.What is the process for return or replacement of MAX1856EUB+TG51?
All MAX1856EUB+TG51 units undergo pre-shipment inspection (PSI). If there is an issue with MAX1856EUB+TG51, 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 MAX1856EUB+TG51 part is unused and in its original packaging.
Return procedure for MAX1856EUB+TG51:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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