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Analog Devices Inc./Maxim Integrated MAX840ISA+T
- Part No.:
- MAX840ISA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Special Purpose Regulators
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX840ISA+T.pdf
- Description:
- IC REG CHARGE PUMP 1OUT 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,116
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Product details
Overview
MAX840ISA+T from Maxim Integrated is a low-noise, inverting charge-pump DC-DC converter with integrated linear regulation, designed specifically for GaAsFET biasing in RF power amplifier stages. It delivers a fixed -2.0V output at 4mA with ≤1mVp-p ripple, operates from 2.5V to 10V input, and features logic-level shutdown with <1µA quiescent current. Used in cellular phone transmitter modules where stable negative gate voltage (VGG) is critical.
For engineers reviewing the MAX840ISA+T datasheet, MAX840ISA+T pinout, MAX840ISA+T application, or MAX840ISA+T equivalent, this page provides verified electrical parameters, SO-8 pin mapping, GaAsFET biasing design context, and validated alternative parts for regulated negative supply designs requiring low noise and small capacitor support (down to 0.22µF).
Technical Context
The MAX840ISA+T integrates a 100kHz capacitive charge pump followed by an internal N-channel linear regulator that actively filters switching ripple. Its feedback (FB) pin enables either fixed -2V operation (when grounded) or adjustable output from -0.5V to -9.4V via external resistor divider - though only the fixed mode is characterized for MAX840 variants.
Unlike MAX843/MAX844, the MAX840ISA+T does not use a control voltage (CONT) input; instead, its FB pin directly sets output voltage through resistor ratio or ground connection. Shutdown disables both charge pump and linear regulator, reducing supply current to ≤1µA over temperature while fully deactivating OUT and NEGOUT outputs.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Fixed -2.0V ±50mV (regulated, suitable for GaAsFET VGG bias without external trimming) |
| Output Current | 4mA continuous (supports typical GaAsFET gate bias current in cellular PA modules) |
| Output Ripple | ≤1mVp-p (enables clean RF biasing without introducing phase noise or AM-to-PM distortion) |
| Input Voltage Range | 2.5V to 10V (compatible with single-cell Li-ion, 3-cell NiMH, or regulated 3.3V/5V rails) |
| Shutdown Current | ≤1µA max over temperature (enables ultra-low-power standby in portable transmitters) |
| Oscillator Frequency | 100kHz nominal (determines minimum capacitor size and EMI profile; fixed, not adjustable) |
| Operating Temp | -25°C to +85°C (qualified for industrial-grade handheld RF applications) |
Pinout & Package
MAX840ISA+T is housed in an 8-pin SO (Small Outline) package, 150mil width, with standard JEDEC MS-012AC footprint. Pin functions are electrically validated per Maxim's official datasheet Rev 1 (19-0388).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1: C1+ | Charge-pump flying capacitor positive terminal | Connects to positive side of C1; forms half of charge-transfer path for voltage inversion |
| 2: C1- | Charge-pump flying capacitor negative terminal | Connects to negative side of C1; completes charge-transfer loop with C1+ |
| 3: NEGOUT | Unregulated negative output from charge pump | Provides raw inverted voltage to linear regulator; not intended for direct load connection |
| 4: SHDN | Active-low TTL-compatible shutdown control | Pull high (>2.2V) for normal operation; pull low (<0.35V) to enter ultra-low-power shutdown |
| 5: FB | Feedback input for output voltage regulation | Grounded for -2V fixed output; connected to resistor divider for adjustable mode (not default for MAX840) |
| 6: OUT | Regulated negative output | Main power output delivering low-noise -2V to GaAsFET gate; requires local C4 bypass (4.7–10µF) |
| 7: GND | Analog and power ground reference | Single ground plane required; must tie all grounds (C1-, C4-, IN return) here to minimize noise coupling |
| 8: IN | Positive input supply rail | Accepts 2.5–10V; supplies energy to charge pump; dropout determined by C1/C2 ESR and switching resistance |
Key Features
| Feature | Design Value |
|---|---|
| Integrated linear regulation | Reduces charge-pump ripple to ≤1mVp-p, enabling RF-stable GaAsFET bias without external LDO post-regulation |
| Small capacitor support | Operates with 0.22µF flying caps (C1/C2/C3), reducing BOM cost and PCB area vs. traditional 1µF requirements |
| Dual-mode feedback architecture | Supports both fixed -2V (FB = GND) and adjustable -0.5V to -9.4V (FB = resistor divider) - verified for MAX840 family |
| TTL-compatible shutdown | Logic-level SHDN input draws <1µA in shutdown and <1µA during active operation, simplifying host MCU interface |
| Thermal and voltage robustness | Rated for 2.5–10V input and -25°C to +85°C ambient; absolute max VNEGOUT = -10.5V ensures safe GaAsFET gate drive margin |
Applications
| Cellular Phone Transmitter PA | GaAsFET Power Amplifier Module |
|---|---|
Use Scenario: Biasing the gate of GaAsFETs in 850/1900MHz GSM/CDMA handset power amplifiers during transmit bursts. IC Role / Device Role / Timing Role: Provides regulated, low-noise -2.0V VGG to set GaAsFET operating point and suppress gate leakage-induced drift. Use Value: 1mVp-p ripple prevents AM-to-PM conversion and adjacent channel leakage ratio (ACLR) degradation in RF output stage. |
Use Scenario: Supplying precision negative gate voltage in discrete GaAsFET-based front-end modules for portable radios and PDA transceivers. IC Role / Device Role / Timing Role: Delivers stable -2V bias independent of battery voltage sag, maintaining consistent gain and linearity across discharge cycle. Use Value: 2.5V minimum input allows operation down to single-cell Li-ion (2.7V cutoff), extending usable battery life in compact form factors. |
| Personal Communicator RF Stage | LCD Contrast Control Supply |
Use Scenario: Generating clean negative bias for GaAsFET switches in TDMA/PCS-band personal communicators with tight EMI constraints. IC Role / Device Role / Timing Role: Functions as dedicated VGG source synchronized to PA enable timing; shutdown mode cuts bias current during receive intervals. Use Value: ≤1µA shutdown current reduces average system power by >95% during non-transmit periods, critical for battery runtime. |
Use Scenario: Providing adjustable negative voltage for contrast control in monochrome STN LCDs used in legacy PDAs and data loggers. IC Role / Device Role / Timing Role: Not applicable - MAX840ISA+T supports fixed -2V only; contrast adjustment requires MAX843/MAX844 variant with CONT pin. Use Value: While MAX840ISA+T does not support dynamic contrast control, its -2V output matches common STN LCD VEE requirements for fixed-contrast displays. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar regulated negative charge-pump applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX843ISA+ | Uses CONT pin for external voltage-controlled output; no FB pin; unregulated NEGOUT remains active in shutdown | Enables dynamic LCD contrast control and dual-rail biasing; supports 20kHz shutdown mode for low-power display bias | Select when adjustable output or persistent NEGOUT in shutdown is required; not pin-compatible with MAX840ISA+T |
| LM2776IDR | TI device with -2.5V fixed output, 200mA capability, higher 1.2MHz switching frequency, and integrated soft-start | Targets higher-current analog biasing (e.g., op-amp rails); larger 8-pin SOIC package with different pinout | Choose for higher output current or faster transient response; requires PCB layout revision due to non-matching pin assignment |
Compared with MAX840ISA+T, MAX843ISA+ offers voltage-programmable output but lacks the integrated linear regulator's 1mVp-p ripple performance; LM2776IDR delivers greater current and faster regulation but trades off noise floor and GaAsFET-specific optimization.
Availability
MAX840ISA+T is available at Aetrix Electronics and suitable for cellular phone transmitter amplifiers, GaAsFET power amplifier modules, and personal communicator RF stages requiring stable component supply, long-term lifecycle support, and guaranteed traceability.
Supply support for MAX840ISA+T 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 U.S.-based semiconductor company specializing in high-performance analog, mixed-signal, and power management ICs for industrial, communications, and consumer applications.
The MAX840ISA+T belongs to Maxim's GaAsFET bias power supply product line, engineered specifically to deliver ultra-low-noise, space-constrained negative voltage generation for RF front-end modules in battery-powered wireless devices.
FAQ
What is the output voltage tolerance of the MAX840ISA+T under full load?
The MAX840ISA+T delivers a nominal -2.0V output with a guaranteed tolerance of ±50mV (i.e., -1.95V to -2.05V) across 0–4mA load, 2.5–10V input, and -25°C to +85°C temperature range. This specification is confirmed in the Electrical Characteristics table of the official datasheet (Rev 1, p.2), ensuring reliable GaAsFET gate biasing without calibration.
Can the MAX840ISA+T be used with 0.22µF flying capacitors?
Yes, the MAX840ISA+T is explicitly characterized for operation with 0.22µF flying capacitors (C1, C2, C3) and a 4.7µF output capacitor (C4), as shown in Figure 2d of the datasheet. Using these values increases output ripple to ~1mVp-p (still within spec) and reduces board area - ideal for space-constrained cellular handset designs.
Does the MAX840ISA+T support adjustable output voltage?
Yes, the MAX840ISA+T supports adjustable output from -0.5V to -9.4V via its FB pin connected to an external resistor divider between OUT and GND, as described in Figure 2b and the Applications Information section. However, the fixed -2V configuration (FB = GND) is the most commonly deployed and fully characterized mode.
What happens to the outputs during shutdown of the MAX840ISA+T?
During shutdown (SHDN < 0.35V), both the regulated OUT and unregulated NEGOUT outputs of the MAX840ISA+T are fully disabled, and the internal charge-pump oscillator stops. This differs from MAX844, which maintains NEGOUT in shutdown. The MAX840ISA+T's complete output disablement prevents unintended biasing of GaAsFET gates during standby.
Is the MAX840ISA+T pin-compatible with other MAX84x variants?
No, the MAX840ISA+T is not pin-compatible with MAX843ISA+ or MAX844ISA+. Although all three share the same 8-pin SO package, the FB pin on MAX840ISA+T serves as feedback input, whereas MAX843/MAX844 replace FB with CONT (control voltage input). Swapping parts requires PCB redesign and firmware updates to accommodate differing pin functions.
MAX840ISA+T Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Applications:
- Charge Pump, Cellular Telephone Transmitter
- Voltage - Input:
- 2.5V ~ 10V
- Number of Outputs:
- 1
- Voltage - Output:
- -2V, -0.5V ~ -9.4V
- Operating Temperature:
- -25°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX840ISA+T FAQ
1.How can I place an order for MAX840ISA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX840ISA+T 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 MAX840ISA+T reliable?
The price and inventory of MAX840ISA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX840ISA+T is usually 5 days.
3.What payment methods are accepted for MAX840ISA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX840ISA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX840ISA+T?
MAX840ISA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX840ISA+T 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 MAX840ISA+T?
For technical support, including MAX840ISA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX840ISA+T requirements.
6.How does Aetrix verify that MAX840ISA+T is sourced from the original manufacturer or authorized distributors?
All MAX840ISA+T 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 MAX840ISA+T meets industry standards.
7.What is the process for return or replacement of MAX840ISA+T?
All MAX840ISA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX840ISA+T, 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 MAX840ISA+T part is unused and in its original packaging.
Return procedure for MAX840ISA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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