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Analog Devices Inc./Maxim Integrated MAX851ISA+
- Part No.:
- MAX851ISA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX851ISA+.pdf
- Description:
- IC REG CHG PUMP ADJ/-1.28V 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,968
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Product details
Overview
MAX851ISA+ from Maxim Integrated is a low-noise, inverting, regulated charge-pump DC-DC converter designed to generate a stable -4.1V output at up to 5mA for GaAsFET biasing in cellular transmitter amplifiers. It operates from 4.5V to 10V input, features 2mVp-p output ripple, 100kHz fixed switching frequency, and logic-level shutdown with ≤5µA max shutdown current over temperature.
For engineers reviewing the MAX851ISA+ datasheet, MAX851ISA+ pinout, MAX851ISA+ application, or MAX851ISA+ equivalent, this device is selected for precision negative bias generation where ultra-low noise, compact SO-8 footprint, and guaranteed -4.1V regulation under load are critical - especially in RF front-end power-amplifier modules requiring stable VGG.
Technical Context
The MAX851ISA+ implements a two-stage architecture: a capacitive charge-pump inverter followed by an internal N-channel linear regulator. The charge-pump generates an unregulated negative voltage at NEGOUT, which the post-regulator conditions to deliver a precise, low-noise -4.1V at OUT when FB is grounded. Its fixed-output configuration eliminates external feedback components.
Unlike the MAX850 (active-low SHDN) and MAX852 (external OSC input), the MAX851ISA+ uses an active-high TTL-compatible shutdown input on Pin 4, enabling direct interface with microcontroller GPIOs. Shutdown reduces supply current to ≤5µA across -25°C to +85°C, supporting battery-sensitive portable RF systems.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed -4.1V (±0.1V), factory-trimmed for GaAsFET VGG bias without external resistors |
| Output Current | 5mA continuous - sufficient to bias typical GaAsFET gate networks while maintaining regulation |
| Input Voltage Range | 4.5V to 10.0V - compatible with 4-cell alkaline/NiMH or single Li-ion with LDO pre-regulation |
| Output Ripple | 2mVp-p max - achieved via integrated linear regulator, critical for minimizing RF amplifier phase noise |
| Switching Frequency | 100kHz fixed - avoids AM radio band interference and simplifies EMI filtering |
| Shutdown Current | ≤5µA max over -25°C to +85°C - enables long standby time in handheld transmitters |
| Supply Current | 3.0mA max - ensures minimal quiescent drain on primary power rail during active operation |
Pinout & Package
MAX851ISA+ is housed in an 8-pin SO (Small Outline) package, 3.9mm × 4.9mm body, 1.27mm pitch, JEDEC MS-012AC compliant. Thermal resistance θJA = 170°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1: IN | Positive power supply input | Accepts 4.5V–10V DC; must be decoupled with ≥1µF low-ESR capacitor near pin |
| 2: GND | Analog/digital ground reference | Common return for charge pump, regulator, and shutdown logic; requires solid ground plane |
| 3: OUT | Regulated negative output | Delivers final -4.1V to GaAsFET gate; connects directly to VGG node with local 10µF low-ESR capacitor |
| 4: SHDN | Active-high shutdown control | Drives internal circuitry into ultra-low-power state when pulled low; TTL-compatible threshold (VIH = 2.0V min) |
| 5: NEGOUT | Unregulated negative charge-pump output | Intermediate node at ~-(VIN − 1V); not user-accessible - feeds internal linear regulator |
| 6: C1− | Negative terminal of flying capacitor C1 | Completes charge-pump inversion cycle; requires 1µF ceramic/tantalum with ≤0.8Ω ESR |
| 7: C1+ | Positive terminal of flying capacitor C1 | Switches between IN and NEGOUT; critical path for charge transfer efficiency and EMI |
| 8: FB | Feedback input (grounded for fixed mode) | Internally connected to -1.28V reference; grounding fixes VOUT = -4.1V per VOUT = -1.28V × (1 + R2/R1) |
Key Features
| Feature | Design Value |
|---|---|
| Fixed -4.1V Output | Factory-trimmed reference eliminates external resistor network, reducing BOM count and layout sensitivity |
| 2mVp-p Output Ripple | Integrated linear regulator suppresses charge-pump switching noise, preserving RF amplifier linearity |
| Active-High TTL SHDN | Direct GPIO compatibility enables simple microcontroller-controlled bias enable/disable without level-shifting |
| 100kHz Fixed Oscillator | Stable internal clock avoids external component tolerance drift and simplifies EMI compliance testing |
| SO-8 Package | Standard surface-mount footprint supports automated assembly and thermal performance suitable for handheld PCBs |
Applications
| Cellular Transmitter Amplifiers | LCD Contrast Bias Control |
|---|---|
Use Scenario: Biasing gate voltage (VGG) of GaAsFET power amplifiers in GSM/EDGE handset RF front-ends. IC Role / Device Role / Timing Role: Provides stable, low-noise negative supply to set FET operating point and optimize gain/efficiency. Use Value: 2mVp-p ripple prevents AM-to-PM conversion in PA stages, directly improving adjacent channel leakage ratio (ACLR). | Use Scenario: Generating adjustable negative bias for LCD segment drivers in portable PDAs and communicators. IC Role / Device Role / Timing Role: Delivers clean, regulated -4.1V to control liquid crystal contrast without flicker or ghosting. Use Value: Fixed output eliminates trimming steps during manufacturing; SO-8 footprint fits tight display module layouts. |
| Wireless Data Loggers | Personal Communicators |
Use Scenario: Powering low-current sensor interface circuits requiring isolated negative bias in battery-operated field units. IC Role / Device Role / Timing Role: Supplies regulated negative rail for op-amp biasing and ADC reference conditioning. Use Value: ≤5µA shutdown current extends battery life over multi-month deployment cycles without sacrificing startup speed. | Use Scenario: Providing GaAsFET gate bias in dual-mode (cellular + Bluetooth) handheld devices with shared power architecture. IC Role / Device Role / Timing Role: Enables fast, synchronized enable/disable of RF power stages during mode transitions. Use Value: Active-high SHDN allows direct control from baseband processor, eliminating discrete logic and reducing system latency. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar negative charge-pump regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX850ISA+ | Active-low SHDN input; identical -4.1V output, ripple, and package | Requires inverted control signal; suited for legacy designs using open-collector drivers | Select when existing firmware/hardware drives SHDN low to enable - no change to bias network or layout |
| LM27761DSGR | Adjustable -1.5V to -5.5V output; 2.5MHz switching; higher IQ (2.5mA typ) | Supports dynamic VGG tuning but adds external resistor divider and higher EMI risk | Choose only if variable bias voltage is required; verify 2.5MHz noise does not interfere with RF bands |
Compared with MAX850ISA+, the MAX851ISA+ simplifies control logic with active-high SHDN, while LM27761DSGR trades fixed precision for flexibility at the cost of increased design complexity and potential RF coupling issues.
Availability
MAX851ISA+ is available at Aetrix Electronics and suitable for cellular phone RF modules, portable LCD displays, and wireless data loggers requiring stable component supply with guaranteed -25°C to +85°C industrial temperature operation.
Supply support for MAX851ISA+ 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 industrial, communications, and consumer applications.
The MAX850–MAX853 family was engineered specifically for low-noise GaAsFET biasing in portable RF transmitters, prioritizing ripple suppression, compact size, and seamless integration into space-constrained handset PCBs.
FAQ
What is the output voltage tolerance of the MAX851ISA+ under full 5mA load?
The MAX851ISA+ delivers -4.1V ±0.1V across its full operating temperature range (-25°C to +85°C) and input voltage range (4.5V to 10V) at 5mA load. This tolerance is guaranteed by factory trimming of the internal -1.28V reference and feedback amplifier, ensuring consistent GaAsFET gate bias without external calibration.
Can the MAX851ISA+ be used with a 3.3V input supply?
No - the MAX851ISA+ requires a minimum 4.5V input to maintain regulation at -4.1V output. At VIN < 4.5V, the internal charge pump cannot generate sufficient headroom for the post-regulator stage, causing output droop or loss of regulation. For 3.3V systems, consider the MAX863 or MAX881R families instead.
How does the MAX851ISA+ achieve 2mVp-p output ripple?
The MAX851ISA+ achieves 2mVp-p output ripple through cascaded noise reduction: first, the 100kHz charge-pump inverter generates a coarse negative voltage at NEGOUT; second, an internal N-channel linear regulator filters this signal, rejecting >60dB of switching noise. This dual-stage architecture is validated in Figure 2a and Typical Operating Characteristics plots.
Is the MAX851ISA+ pin-compatible with the MAX850ISA+?
No - although both use the same SO-8 package and share identical pin functions for IN, GND, OUT, NEGOUT, C1−, C1+, and FB, the MAX851ISA+ has active-high SHDN on Pin 4, whereas the MAX850ISA+ has active-low SHDN on Pin 4. Swapping them without inverting the control signal will cause functional failure.
What external capacitors are required for stable operation of the MAX851ISA+?
The MAX851ISA+ requires four external capacitors: C1 and C2 (1µF, ≤0.8Ω ESR ceramic/tantalum) for charge pumping; C3 (1µF, low-ESR) on IN; and C4 (10µF, ≤0.2Ω ESR) on OUT. These values are specified in Figures 2a and 2b of the datasheet and are essential to maintain low dropout, ripple suppression, and transient response.
MAX851ISA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Negative
- Topology:
- Charge Pump
- Output Type:
- Adjustable (Fixed)
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.5V
- Voltage - Input (Max):
- 10V
- Voltage - Output (Min/Fixed):
- -1.28V (-4.1V)
- Voltage - Output (Max):
- -9V
- Current - Output:
- 5mA
- Frequency - Switching:
- 100kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -25°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX851ISA+ FAQ
1.How can I place an order for MAX851ISA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX851ISA+ 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 MAX851ISA+ reliable?
The price and inventory of MAX851ISA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX851ISA+ is usually 5 days.
3.What payment methods are accepted for MAX851ISA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX851ISA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX851ISA+?
MAX851ISA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX851ISA+ 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 MAX851ISA+?
For technical support, including MAX851ISA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX851ISA+ requirements.
6.How does Aetrix verify that MAX851ISA+ is sourced from the original manufacturer or authorized distributors?
All MAX851ISA+ 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 MAX851ISA+ meets industry standards.
7.What is the process for return or replacement of MAX851ISA+?
All MAX851ISA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX851ISA+, 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 MAX851ISA+ part is unused and in its original packaging.
Return procedure for MAX851ISA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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