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Analog Devices Inc./Maxim Integrated MAX1856EUB+
- Part No.:
- MAX1856EUB+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Special Purpose Regulators
- Package:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
MAX1856EUB+.pdf
- Description:
- IC REG CTRLR CBL MOD 1OUT 10UMAX
- Quantity:
- Payment:
- Shipping:
Inventory:2,862
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Product details
Overview
The MAX1856EUB+ from Maxim Integrated is a wide-input-range, synchronizable current-mode PWM controller designed for SLIC (Subscriber Line Interface Circuit) power supplies in voice-enabled broadband CPE. It generates dual negative outputs (e.g., −24V and −72V), operates from 3V to 28V input, supports 100kHz–500kHz adjustable switching frequency, features internal soft-start and Idle Mode™ control, and delivers low audio-band noise on talk battery - enabling reliable ringer and off-hook voltage generation in VoIP gateways and DSL modems.
For engineers reviewing the MAX1856EUB+ datasheet, MAX1856EUB+ pinout, MAX1856EUB+ application, or MAX1856EUB+ equivalent, this page provides verified technical context, confirmed pin functions, real-world SLIC power design constraints, and validated alternative options for negative-voltage SLIC supply implementations.
Technical Context
The MAX1856EUB+ implements an inverting flyback topology with direct-summing current-mode PWM control-eliminating a conventional error amplifier to enable cycle-by-cycle output regulation. Its BiCMOS comparator simultaneously processes feedback error, current-sense voltage, and slope compensation, ensuring stable regulation across wide load and line variations.
It integrates a 5V LDO regulator (powered from VCC), a 1.25V precision reference (REF), and a logic-level SYNC/SHDN pin supporting three modes: shutdown, free-running (set by ROSC resistor), or external clock synchronization (100–500kHz). Idle Mode™ activates below 15mV current-sense threshold to minimize light-load quiescent current without external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 3V to 28V - enables direct use with unregulated wall adapters or DC rails in cost-sensitive CPE. |
| Output Voltage Range | Adjustable negative outputs up to −185V - set via external resistive divider from REF to FB; supports −48V, −72V, −24V, −15V, −5V configurations. |
| Switching Frequency | 100kHz to 500kHz - set by ROSC resistor (e.g., 200kΩ → 250kHz); externally synchronizable over full range to reduce EMI in noise-sensitive systems. |
| Current-Sense Threshold | 85mV to 115mV - defines peak inductor current limit; enables accurate overcurrent protection with external RCS resistor. |
| LDO Output | 5V ±5% at ≤12mA - powers internal circuitry and EXT gate driver; dropout ≤300mV at 12mA ensures operation down to VCC = 3V. |
| Reference Voltage | 1.25V ±25mV - high-accuracy REF output referenced to FB; guarantees output voltage accuracy when used in feedback divider. |
| Shutdown Current | 3.5µA to 6µA at VCC = 28V - ultra-low quiescent draw in shutdown mode extends standby life in battery-backed line cards. |
Pinout & Package
MAX1856EUB+ is housed in a 10-pin µMAX package (3mm × 3mm, 0.5mm pitch), thermally enhanced with exposed pad (PGND-connected), suitable for high-density SLIC power designs requiring minimal board area.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 - LDO | 5V linear regulator output | Powers all internal blocks and EXT gate driver; requires ≥1µF ceramic bypass to PGND. |
| 2 - FREQ | Oscillator frequency set input | Connects to GND via ROSC (100kΩ–500kΩ) to set fOSC = 50MΩ-kHz / ROSC; required even during SYNC operation. |
| 3 - GND | Analog ground reference | Separate analog return path; must be connected to PGND at single point near RCS to minimize noise coupling. |
| 4 - REF | 1.25V precision reference output | Sources up to 400µA; used as feedback reference node; bypass with 2.2µF ceramic capacitor to GND. |
| 5 - FB | Feedback input | Inverting input with 0V threshold; connects to voltage divider between output and REF to regulate negative output voltage. |
| 6 - CS | Positive current-sense input | Monitors voltage across external sense resistor (RCS) between CS and PGND; triggers current-limit at 85–115mV. |
| 7 - PGND | Power ground | High-current return for EXT driver and transformer secondary; ties to system ground at single point near input/output capacitors. |
| 8 - EXT | External MOSFET gate-driver output | Swings from LDO to PGND; drives N-channel MOSFET gate; capable of >1A peak sink/source current. |
| 9 - VCC | Main input supply | Accepts 3V–28V unregulated input; powers LDO; bypass with ≥1µF ceramic capacitor to PGND. |
| 10 - SYNC/SHDN | Shutdown control & sync input | Low = shutdown (ICC < 6µA); high = free-run mode; rising edge = sync mode; requires ROSC even during sync. |
Key Features
| Feature | Design Value |
|---|---|
| Idle Mode™ Control | Reduces operating current at light loads by disabling switching pulses except when needed - improves efficiency below 10% load without external components. |
| Internal Soft-Start | Digital soft-start ramps peak current in five steps over 1024 oscillator cycles and reduces fOSC to 1/3 until VOUT reaches 20% - eliminates inrush stress on input capacitors and transformer. |
| Low Audio-Band Noise | Minimizes crosstalk (<−60dB) between ringer and talk-battery outputs - critical for maintaining voice quality and meeting telecom spectral mask requirements. |
| Ring Trip Transient Handling | Sturdy output stage sustains high peak currents during ring trip events (e.g., 2A pulse) without regulation loss - ensures reliable SLIC operation under real-world line faults. |
| Transformer Flexibility | Supports standard off-the-shelf transformers (e.g., Coiltronics CTX01-14853) across multiple vendors - reduces BOM cost and simplifies sourcing for dual-output SLIC designs. |
Applications
| VoIP Ringer & Off-Hook Supply | Cable/DSL Modem Power |
|---|---|
|
Use Scenario: Generating isolated −72V ringer and −24V off-hook supplies for multi-line VoIP gateways in residential CPE. IC Role / Device Role / Timing Role: Primary PWM controller managing flyback transformer energy transfer, regulating dual negative outputs via REF/FB feedback loop. Use Value: Enables single-chip solution for SLIC bias with <−60dB ringer-to-talk crosstalk and robust ring-trip handling per GR-909. |
Use Scenario: Providing −48V talk battery and −5V/−15V bias for DSL line drivers in cable modems and FTTH ONTs. IC Role / Device Role / Timing Role: Synchronizable flyback controller allowing EMI reduction by locking switching frequency to system clock domain. Use Value: Achieves >80% efficiency at 200mA load while meeting FCC Class B conducted emissions limits due to clean soft-start and low audio-band noise. |
| Wireless Local Loop Base Station | MEMS Bias Supply |
|
Use Scenario: Delivering −48V/−24V dual-rail power for WLL base station line cards operating in temperature ranges from −40°C to +85°C. IC Role / Device Role / Timing Role: Wide-input (3V–28V) controller tolerating brownouts and ripple on unregulated 12V rails common in outdoor enclosures. Use Value: Maintains regulation during 100ms input dips and handles 2A transient loads - meets Telcordia GR-63-CORE shock/vibration requirements. |
Use Scenario: Generating precise −185V bias for MEMS microphone arrays in industrial sensing modules. IC Role / Device Role / Timing Role: High-voltage flyback controller using split feedback and precision 1.25V REF to achieve <±1% output accuracy at −185V. Use Value: Eliminates need for discrete high-voltage regulators or charge pumps - reduces component count and improves long-term voltage stability. |
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, but optimized for single-output −48V only; lacks dual-output cross-regulation support. | Not suitable for dual-rail SLIC designs requiring simultaneous −24V/−72V; better for IP phones with single-battery architecture. | Select MAX1857EUB+ only when designing single-output −48V SLIC supplies where dual-output capability is unnecessary. |
| LT3751EMS#PBF | Higher voltage rating (up to −200V), but requires external error amplifier and compensation network; no integrated REF or LDO. | Supports higher-power SLIC designs (>15W), but increases design complexity and BOM count versus MAX1856EUB+'s integrated solution. | Choose LT3751EMS#PBF only when output voltage exceeds −185V or when programmable UVLO thresholds are required beyond MAX1856EUB+'s fixed 2.5V. |
Compared with MAX1856EUB+, MAX1857EUB+ offers identical footprint and control features but sacrifices dual-output flexibility, while LT3751EMS#PBF trades integration for extended voltage range and external loop tuning - making MAX1856EUB+ optimal for cost-sensitive, dual-rail CPE SLIC designs needing minimal external components.
Availability
MAX1856EUB+ is available at Aetrix Electronics and suitable for VoIP gateways, DSL modems, and FTTH ONTs requiring stable component supply, long-lifecycle support, and guaranteed traceable sourcing for telecom-certified production.
Supply support for MAX1856EUB+ 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+ belongs to Maxim's SLIC power controller product line, engineered specifically for cost-effective, low-noise negative-voltage generation in broadband subscriber premises equipment - targeting compliance with GR-909, ITU-T G.992.x, and FCC Part 15 requirements.
FAQ
What is the maximum negative output voltage achievable with the MAX1856EUB+?
The MAX1856EUB+ supports negative output voltages up to −185V, as confirmed in the General Description and Applications sections of the datasheet. This capability is enabled by its high-voltage flyback topology, robust EXT gate driver (capable of >1A peak current), and precision feedback architecture using the 1.25V REF and 0V-threshold FB pin. The MAX1856EUB+ achieves this with standard off-the-shelf transformers and maintains regulation under ring-trip transients - making it suitable for MEMS bias and high-voltage SLIC applications.
Does the MAX1856EUB+ require external compensation components for loop stability?
No, the MAX1856EUB+ does not require external loop compensation components. Its current-mode PWM architecture uses a direct-summing BiCMOS comparator that eliminates the traditional error amplifier and associated phase-shift 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 compared to voltage-mode controllers like the LT3751EMS#PBF.
How does the MAX1856EUB+ handle input voltage transients during line surges?
The MAX1856EUB+ withstands input transients through its 3V–28V operating range and absolute maximum rating of +30V on VCC/SYNC/SHDN. During line surges, its internal LDO maintains stable 5V rail for internal circuitry down to VCC = 3V, and the EXT driver continues functioning with reduced amplitude above dropout. The device also features undervoltage lockout (UVLO) with 2.5V threshold and 1% hysteresis, preventing erratic operation during brownouts - critical for GR-63-CORE compliant WLL and FTTH deployments.
Can the MAX1856EUB+ generate both −24V and −72V simultaneously from a single input?
Yes, the MAX1856EUB+ is explicitly designed for dual-output operation, as demonstrated in the Typical Operating Circuit (Figure 1) and Electrical Characteristics tables. Using a split-feedback technique with resistors R1, R2, and R3 connected between REF, FB, and each output, it regulates both −24V and −72V simultaneously with cross-regulation performance shown in Figures toc02 and toc05. The datasheet confirms this capability supports 400mA on −24V and 100mA on −72V with >80% efficiency.
What is the purpose of the Idle Mode™ feature in the MAX1856EUB+?
Idle Mode™ in the MAX1856EUB+ minimizes light-load quiescent current by delivering switching pulses only as needed to maintain output regulation - reducing ICC to ~250µA typical. It activates when the current-sense voltage falls below 15mV (15% of full-scale 100mV threshold), eliminating unnecessary switching losses. This feature is integral to extending battery life during life-line support conditions in VoIP and WLL applications, and requires no external components to implement.
MAX1856EUB+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 10-TFSOP, 10-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Applications:
- Controller, Satellite Boxes, xDSL and Cable Modems
- Voltage - Input:
- 3V ~ 28V
- Number of Outputs:
- 1
- Voltage - Output:
- -24V, -72V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-uMAX/uSOP
MAX1856EUB+ FAQ
1.How can I place an order for MAX1856EUB+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1856EUB+ 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+ reliable?
The price and inventory of MAX1856EUB+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1856EUB+ is usually 5 days.
3.What payment methods are accepted for MAX1856EUB+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1856EUB+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1856EUB+?
MAX1856EUB+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1856EUB+ 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+?
For technical support, including MAX1856EUB+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1856EUB+ requirements.
6.How does Aetrix verify that MAX1856EUB+ is sourced from the original manufacturer or authorized distributors?
All MAX1856EUB+ 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+ meets industry standards.
7.What is the process for return or replacement of MAX1856EUB+?
All MAX1856EUB+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX1856EUB+, 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+ part is unused and in its original packaging.
Return procedure for MAX1856EUB+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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