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Analog Devices Inc./Maxim Integrated MAX1856EUB+TG05
- Part No.:
- MAX1856EUB+TG05
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Special Purpose Regulators
- Package:
- -
- Datasheet:
-
MAX1856EUB+TG05.pdf
- Description:
- INTEGRATED CIRCUIT
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Product details
Overview
MAX1856EUB+TG05 from Maxim Integrated is a wide-input-range, synchronizable current-mode PWM controller for SLIC ringer and off-hook power supplies. It supports dual-output configurations (e.g., −24V/−72V), operates from 3V to 28V input, delivers up to 400mA on −24V and 100mA on −72V, and features adjustable 100kHz–500kHz switching frequency with external resistor or clock sync - used in VoIP CPE, DSL modems, and FTTH line cards.
For engineers reviewing the MAX1856EUB+TG05 datasheet, MAX1856EUB+TG05 pinout, MAX1856EUB+TG05 application, or MAX1856EUB+TG05 equivalent, key selection criteria include its flyback topology support for negative high-voltage generation, internal soft-start, Idle Mode™ light-load efficiency, low audio-band noise on talk battery, and compatibility with off-the-shelf transformers from Coiltronics, ICE Components, and Pulse Engineering.
Technical Context
The MAX1856EUB+TG05 implements an inverting flyback controller with direct-summing BiCMOS PWM comparator-eliminating traditional error amplifiers for cycle-by-cycle output regulation. Its current-mode control uses a 100mV current-sense threshold and slope compensation, enabling stable operation without external loop compensation.
It integrates a 5V LDO regulator (2.7V–5.5V output range, 12mA max) powered from VCC, supports logic-level shutdown via SYNC/SHDN, and provides internal soft-start with 1/5th-to-full current ramp over 1024 oscillator cycles. Idle Mode™ activates below 15mV sensed current to minimize quiescent draw at light loads.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 28V - enables direct use with unregulated wall adapters and low-cost DC supplies in xDSL/CPE systems. |
| Switching Frequency | 100kHz to 500kHz - set by ROSC resistor or synchronized externally; higher frequencies reduce transformer size but increase core/gate losses. |
| Current-Sense Threshold | 85mV to 115mV - defines peak inductor current limit; enables accurate overcurrent protection without calibration. |
| LDO Output Voltage | 4.50V to 5.50V - powers internal circuitry and EXT gate driver; dropout ≤300mV at 12mA ensures stable bias down to VCC = 3V. |
| FB Reference Voltage | 1.225V to 1.275V - referenced to FB pin (0V threshold); sets output voltage accuracy via external resistive divider. |
| Shutdown Current | 3.5µA to 6µA at VCC = 28V - enables ultra-low-power standby in life-line support applications. |
| Operating Temp Range | −40°C to +85°C - qualified for industrial and broadband CPE environments including LMDS, WLL, and FTTH equipment. |
Pinout & Package
MAX1856EUB+TG05 is housed in a 10-pin µMAX package (3mm × 3mm, 0.5mm pitch), thermally enhanced with exposed pad for improved power dissipation in high-efficiency SLIC supplies.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| LDO (Pin 1) | 5V linear regulator 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 program fOSC = 50MΩ-kHz / ROSC; required even during SYNC mode. |
| GND (Pin 3) | Analog ground reference | Reference node for FB, REF, CS; must be separated from PGND at single point near RCS to avoid noise coupling. |
| 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 | Voltage threshold = 0V; connects to resistive divider between output and REF to regulate negative output voltages. |
| CS (Pin 6) | Positive current-sense input | Monitors voltage across external sense resistor (RCS) between CS and PGND; triggers current-limit at ~100mV. |
| PGND (Pin 7) | Power ground return | High-current return path for MOSFET source, output rectifiers, and RCS; must connect to GND only at RCS Kelvin point. |
| EXT (Pin 8) | External MOSFET gate driver | Swings from LDO to PGND; drives N-channel FET gate; peak current capability supports large gate charges up to 20nC @ 500kHz. |
| VCC (Pin 9) | Input supply to LDO | Accepts 3V–28V unregulated input; bypassed to PGND with ≥1µF ceramic capacitor; powers LDO and internal bias. |
| SYNC/SHDN (Pin 10) | Shutdown control & sync input | Low = shutdown (3.5µA IQ); high = free-running at ROSC-set frequency; rising edge = sync mode (100–500kHz). |
Key Features
| Feature | Design Value |
|---|---|
| Inverting flyback topology support | Enables efficient generation of high negative voltages (up to −185V) for SLIC ringer and MEMS bias without polarity inversion stages. |
| Idle Mode™ light-load control | Reduces operating current below 15mV CS threshold, improving efficiency at <10% load - critical for life-line talk-battery operation. |
| Internal soft-start (no external cap) | Prevents inrush stress on input capacitors and transformer by ramping peak current in 5 steps over 1024 cycles. |
| Adjustable switching frequency | 100kHz–500kHz via ROSC resistor or external clock - allows EMI optimization and transformer size trade-offs in space-constrained CPE. |
| Low audio-band noise on talk battery | Minimizes audible interference in voice paths by suppressing switching harmonics below 20kHz through optimized PWM timing and filtering. |
Applications
| VoIP Ringer Supply | DSL Modem Power |
|---|---|
Use Scenario: Generating −72V ringer and −24V off-hook supplies for multi-line VoIP phones and residential gateways. IC Role / Device Role / Timing Role: Primary PWM controller managing dual-output flyback conversion with cross-regulation between outputs. Use Value: Eliminates need for discrete charge-pump or transformer-based solutions; achieves >80% efficiency at full load with standard off-the-shelf transformers. | Use Scenario: Providing isolated −48V bias for CO line drivers in ADSL/VDSL modems and customer premises routers. IC Role / Device Role / Timing Role: High-voltage negative supply generator with programmable frequency to avoid interference with DSL signal bands. Use Value: Supports 200mA at −48V with <50mV ripple; meets stringent noise requirements for upstream/downstream data integrity. |
| FTTH Line Card | MEMS Bias Supply |
Use Scenario: Powering POTS interfaces in fiber-to-the-home terminal units requiring −48V and −24V rails under life-line conditions. IC Role / Device Role / Timing Role: Dual-rail SLIC power manager with shutdown control and soft-start for hot-swap and brownout resilience. Use Value: Maintains regulated output during AC dropout via wide 3V–28V input range; Idle Mode extends backup battery runtime. | Use Scenario: Delivering up to −185V bias for MEMS microphones and RF switches in next-gen communication modules. IC Role / Device Role / Timing Role: High-voltage flyback controller with precise current sensing and slope compensation for stable high-impedance loads. Use Value: Enables single-chip solution for >100V negative bias without cascaded converters; supports adjustable output via feedback divider. |
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 architecture; supports single-output (−48V or −72V only) instead of dual-output; lacks dual-feedback capability. | Used where only one high-voltage rail is needed (e.g., IP phones), not dual-rail SLIC systems. | Select MAX1857EUB+ when designing for cost-sensitive single-output applications without cross-regulation requirements. |
| LT3751EMS#PBF | Wide-input flyback controller with integrated high-side switch; no internal LDO; requires external bias supply; supports higher output voltages (>−200V). | Targeted at industrial high-voltage bias supplies, not telecom SLIC compliance; lacks Idle Mode and talk-battery noise optimization. | Choose LT3751EMS#PBF for non-telecom high-voltage applications needing integrated switch and >−200V capability, not SLIC-specific features. |
Compared with MAX1857EUB+, MAX1856EUB+TG05 provides true dual-output regulation with split feedback, essential for ringer/talk-battery separation. Versus LT3751EMS#PBF, it offers built-in LDO, lower audio-band noise, and Idle Mode - making it purpose-built for telecom SLIC compliance rather than general high-voltage bias.
Availability
MAX1856EUB+TG05 is available at Aetrix Electronics and suitable for VoIP gateways, DSL modems, and FTTH line cards requiring stable component supply, long-term lifecycle support, and consistent parametric performance across temperature and load.
Supply support for MAX1856EUB+TG05 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) designs precision analog, mixed-signal, and power management ICs for communications, computing, and industrial applications.
The MAX1856 belongs to Maxim's SLIC power supply controller product line, engineered specifically for voice-enabled broadband CPE - delivering high-efficiency, low-noise negative voltage generation while supporting legacy telephone interface standards.
FAQ
What is the primary function of the MAX1856EUB+TG05 in telecom power systems?
The MAX1856EUB+TG05 serves as a dedicated current-mode PWM controller for generating negative SLIC power rails - notably −24V (off-hook/talk battery) and −72V (ringer) - using an inverting flyback topology. Its design prioritizes low audio-band noise, ring-trip transient handling, and compatibility with off-the-shelf transformers, making it integral to VoIP CPE, DSL modems, and FTTH terminals. The MAX1856EUB+TG05 integrates an LDO, soft-start, and Idle Mode™ to meet telecom-specific reliability and efficiency demands.
Can the MAX1856EUB+TG05 generate a single −48V output for IP phones?
Yes, the MAX1856EUB+TG05 can generate a regulated −48V output by configuring the feedback network between REF and FB pins using appropriate resistor values. Typical operation at −48V supports up to 200mA with >80% efficiency (VIN = 12V). The MAX1856EUB+TG05 maintains tight line/load regulation and low ripple due to its current-mode control and internal compensation - confirmed in Figure 4 and toc10/toc11 of the datasheet.
How does the SYNC/SHDN pin operate in synchronization mode?
When a clean external clock (100kHz–500kHz) is applied to SYNC/SHDN, the MAX1856EUB+TG05 initiates each switching cycle on the rising edge of that clock - enabling EMI reduction by aligning switching noise away from sensitive bands. The IC still requires the ROSC resistor to be populated, and ROSC should be set to yield an internal frequency ~15% below the sync clock to ensure reliable lock. The MAX1856EUB+TG05 resumes internal oscillation within one cycle if sync is lost while high, or shuts down after 50µs if sync is lost while low.
What transformer specifications are recommended for MAX1856EUB+TG05 in a −24V/−72V dual-output design?
For −24V/−72V dual-output operation, the datasheet recommends Coiltronics CTX01-14853 or ICE Components ICA-0635 - both 1:2:2:2 turns ratio, rated for 12V input and capable of 400mA/−24V and 100mA/−72V. These transformers support >80% efficiency and meet cross-regulation specs (±1.5% load step response). The MAX1856EUB+TG05's flyback topology and current-mode control allow stable operation with these off-the-shelf parts without custom magnetics.
Does the MAX1856EUB+TG05 require external loop compensation components?
No, the MAX1856EUB+TG05 does not require external loop compensation. Its current-mode control architecture with direct-summing comparator eliminates the need for an external error amplifier or compensation network. Stability is inherently achieved through peak current limiting and slope compensation - verified across temperature and line/load variations in the datasheet's typical operating characteristics (toc01–toc19). This simplifies PCB layout and reduces BOM count versus voltage-mode controllers.
MAX1856EUB+TG05 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:
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MAX1856EUB+TG05 FAQ
1.How can I place an order for MAX1856EUB+TG05 through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1856EUB+TG05 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+TG05 reliable?
The price and inventory of MAX1856EUB+TG05 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1856EUB+TG05 is usually 5 days.
3.What payment methods are accepted for MAX1856EUB+TG05?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1856EUB+TG05 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1856EUB+TG05?
MAX1856EUB+TG05 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1856EUB+TG05 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+TG05?
For technical support, including MAX1856EUB+TG05 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1856EUB+TG05 requirements.
6.How does Aetrix verify that MAX1856EUB+TG05 is sourced from the original manufacturer or authorized distributors?
All MAX1856EUB+TG05 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+TG05 meets industry standards.
7.What is the process for return or replacement of MAX1856EUB+TG05?
All MAX1856EUB+TG05 units undergo pre-shipment inspection (PSI). If there is an issue with MAX1856EUB+TG05, 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+TG05 part is unused and in its original packaging.
Return procedure for MAX1856EUB+TG05:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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