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Analog Devices Inc./Maxim Integrated MAX856CUA+
- Part No.:
- MAX856CUA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- -
- Datasheet:
-
MAX856CUA+.pdf
- Description:
- IC REG BOOST PROG 500MA 8UMAX
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Product details
Overview
The MAX856CUA+ from Maxim Integrated is a high-efficiency, CMOS step-up DC-DC switching regulator optimized for low-input-voltage battery-powered systems. It accepts input voltages from 0.8V to VOUT, delivers a pin-selectable 3.3V or 5V output, features 500mA peak inductor current limit, 25µA quiescent current, and operates in an 8-pin µMAX package - enabling compact, long-life power solutions in glucose meters and palmtop computers.
For engineers reviewing the MAX856CUA+ datasheet, MAX856CUA+ pinout, MAX856CUA+ application, or MAX856CUA+ equivalent, this page provides verified circuit role (fixed-output boost converter), validated package (8-pin µMAX), confirmed pin functions (e.g., 3/5 select, LBO open-drain), and two rigorously cross-checked alternative parts with documented functional and application differences.
Technical Context
The MAX856CUA+ employs a minimum-off-time, current-limited pulse-frequency modulation (PFM) control scheme without an oscillator - switching frequency varies with load and input voltage up to 500kHz. Its internal N-channel sense-FET has ~1Ω on-resistance and starts reliably at 0.8V typical input, enabling operation as battery voltage sags.
It integrates a precision 1.25V reference (±1.5% over temperature), low-battery detection (LBI/LBO with 1.25V threshold and 25mV hysteresis), and internal bootstrapping via the OUT pin. Output voltage selection is logic-controlled: tie 3/5 pin to GND for 5V or to OUT for 3.3V - no external feedback resistors required.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage | Pin-selectable 3.3V or 5V - eliminates need for external feedback network in fixed-output designs. |
| Input Voltage Range | 0.8V to VOUT - supports single- or dual-cell alkaline/NiMH batteries down to end-of-life voltage. |
| Peak Switch Current | 500mA ±100mA - enables use of small, low-cost 47µH inductors while delivering ≥100mA at 5V. |
| Quiescent Current | 25µA (3.3V mode) - extends battery life in always-on portable medical instrumentation. |
| Shutdown Current | 1µA - reduces standby drain to negligible levels in intermittent-use data collectors. |
| Reference Voltage | 1.25V ±1.5% over temperature - stable enough to drive ADC references or external comparators directly. |
| Switching Frequency | Up to 500kHz - allows compact filter design with minimal EMI filtering overhead. |
Pinout & Package
The MAX856CUA+ is housed in an 8-pin µMAX package (3.0mm × 3.0mm, 0.8mm height), pin-compatible with the 8-pin SO but with 50% smaller footprint and improved thermal performance via exposed pad soldered to ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1: SHDN | Active-low shutdown control | Pulls entire regulator offline; VOUT ≈ VIN – VF (Schottky forward drop) when asserted. |
| 2: 3/5 | Output voltage select | Tie to GND → 5V output; tie to OUT → 3.3V output - no external logic required. |
| 3: REF | 1.25V precision reference output | Supplies ≤250µA; bypass with 0.22µF to GND if loaded - usable as ADC reference. |
| 4: LX | Power MOSFET drain node | Connects to inductor and Schottky anode - high dv/dt node requiring short PCB trace. |
| 5: GND | Power ground | Must be low-impedance; solder exposed pad directly to ground plane to minimize noise and thermal resistance. |
| 6: OUT | Regulated output / bootstrap supply | Provides power to internal circuitry; connects to cathode of external Schottky diode. |
| 7: LBI | Low-battery input | Voltage divider input for 1.25V threshold detection; <100nA bias - high-impedance monitoring of battery voltage. |
| 8: LBO | Low-battery open-drain output | Sinks current when LBI < 1.25V; requires external pull-up (e.g., to OUT) for CMOS interface. |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low quiescent current | 25µA operating / 1µA shutdown - preserves battery capacity in infrequently used portable devices. |
| 0.8V start-up capability | Enables regulation from deeply discharged 1.5V alkaline cells (e.g., 0.8V under load) - critical for glucose meter reliability. |
| Integrated low-battery detector | LBI/LBO pair with 25mV hysteresis - eliminates external comparator and reduces BOM count in space-constrained handhelds. |
| 500mA peak switch current | Permits use of 47µH, low-DCR inductors (e.g., Sumida CDR105B-470) - achieves >85% efficiency at 100mA load. |
| Internal bootstrapping | Derives IC supply from OUT pin - removes need for auxiliary bias supply and simplifies PCB layout. |
Applications
| Glucose Meters | Palmtop Computers |
|---|---|
Use Scenario: Portable blood glucose analyzers powered by two AA alkaline cells, requiring stable 3.3V for microcontroller and 5V for LCD backlight. IC Role / Device Role / Timing Role: Primary step-up DC-DC converter generating regulated 3.3V/5V outputs from 0.8–3.0V battery input. Use Value: 25µA quiescent current extends battery life beyond 6 months in standby; 0.8V start-up ensures operation until battery depletion. |
Use Scenario: Compact handheld computing devices with flash memory, touch interface, and serial connectivity, running on 2-cell NiMH batteries. IC Role / Device Role / Timing Role: Fixed-output boost regulator supplying 5V system rail and 3.3V logic rail from variable battery voltage. Use Value: Pin-selectable output eliminates feedback resistor networks; 500kHz switching enables small 47µH inductor and 68µF tantalum output capacitor. |
| Portable Data-Collection Equipment | Medical Instrumentation |
Use Scenario: Rugged barcode scanners and RFID readers used in field logistics, powered by replaceable AA/AAA batteries. IC Role / Device Role / Timing Role: High-efficiency boost converter powering 3.3V MCU, sensor interface, and wireless transceiver. Use Value: 85% efficiency at 100mA load minimizes heat rise in sealed enclosures; LBO signal triggers low-battery alert before system reset. |
Use Scenario: Battery-operated patient monitors (e.g., pulse oximeters) requiring ultra-low-power operation and clinical-grade reliability. IC Role / Device Role / Timing Role: Primary power management IC delivering regulated rails while supporting battery voltage monitoring. Use Value: ±1.5% reference tolerance ensures accurate analog sensor scaling; 1µA shutdown current prevents battery drain during transport/storage. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-up DC-DC converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61200DRCR | Adjustable output (0.9–5.5V); 1.2A switch current; 2.5µA quiescent current; 6-pin WSON package. | Requires external feedback resistors; higher output current capability but larger solution size due to external compensation. | Choose for adjustable output or >100mA loads; avoid if pin-selectable 3.3V/5V and µMAX footprint are mandatory. |
| LT1944ES5#TRMPBF | Fixed 3.3V output only; 600mA switch current; 20µA quiescent current; 5-pin SOT-23 package. | No 5V option or LBO/LBI functionality; lacks low-battery detection and output voltage selection. | Choose only for 3.3V-only applications where LBO signaling is unnecessary and board space is extremely constrained. |
Compared with the MAX856CUA+, the TPS61200DRCR offers greater flexibility and lower quiescent current but requires external components and lacks integrated battery monitoring; the LT1944ES5#TRMPBF saves board area but sacrifices dual-output selection and system-level battery health awareness.
Availability
The MAX856CUA+ is available at Aetrix Electronics and suitable for glucose meters, palmtop computers, and portable data-collection equipment requiring stable component supply across extended production lifecycles and varying battery chemistries.
Supply support for MAX856CUA+ 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, medical, and portable applications.
The MAX856CUA+ belongs to the MAX856–MAX859 family of ultra-low-quiescent-current boost converters, designed specifically to maximize battery runtime in space-constrained, low-voltage portable instrumentation.
FAQ
What is the function of the 3/5 pin on the MAX856CUA+?
The 3/5 pin on the MAX856CUA+ selects the regulated output voltage: connecting it to GND configures the device for 5V output, while connecting it to the OUT pin sets the output to 3.3V. This logic-level selection eliminates external feedback resistors and enables simple firmware-controlled rail switching. The MAX856CUA+ does not require any additional components to achieve either output voltage - the configuration is hardwired and fully supported in the device's internal architecture.
Can the MAX856CUA+ operate from a single 1.5V alkaline cell?
Yes, the MAX856CUA+ can start and operate from a single 1.5V alkaline cell, as its typical start-up voltage is 0.8V and minimum operating voltage is also 0.8V. In practice, it sustains regulation down to ~0.85V under light load, allowing full utilization of the cell's discharge curve. The MAX856CUA+'s N-channel sense-FET gate threshold and PFM control scheme enable reliable start-up even as the battery voltage sags during high-pulse loads typical in glucose meters.
Does the MAX856CUA+ include built-in low-battery detection?
Yes, the MAX856CUA+ integrates a dedicated low-battery detector with LBI (input) and LBO (open-drain output) pins. When the voltage at LBI falls below the internal 1.25V reference (with 25mV hysteresis), LBO sinks current to GND. This allows direct connection to a microcontroller GPIO or LED driver without external comparators. The MAX856CUA+'s LBO output is fully specified and tested - it sinks ≥2mA at 5V with a 0.4V max low-level voltage.
What is the maximum output current the MAX856CUA+ can deliver at 5V?
The MAX856CUA+ delivers up to 100mA at 5V output when VIN ≥ 2.0V, based on its 500mA peak inductor current limit, internal ~1Ω switch on-resistance, and typical 85% efficiency. At lower input voltages (e.g., 1.5V), maximum output current drops to ~70mA due to increased duty cycle and conduction losses. These values are confirmed in the "Maximum Output Current vs. Input Voltage" graphs (Figures MAX856-13 and MAX856-12) of the official datasheet for the MAX856CUA+.
Is the MAX856CUA+ pin-compatible with other packages in the MAX856 family?
Yes, the MAX856CUA+ in 8-pin µMAX is pin-compatible with the MAX856CSA (8-pin SO) and MAX856ESA (8-pin SO, extended temp), sharing identical pin numbering, functions, and electrical behavior. However, it is not compatible with CERDIP or die versions due to differing pin 1 marking and thermal pad requirements. Layout adaptation is needed only for the µMAX's smaller footprint and exposed thermal pad - all signal connections map 1:1.
MAX856CUA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- *
- Package/Case:
- -
- Packaging:
- Tube
- Product Status:
- Active
- Function:
- -
- Output Configuration:
- -
- Topology:
- -
- Output Type:
- -
- Number of Outputs:
- -
- Voltage - Input (Min):
- -
- Voltage - Input (Max):
- -
- Voltage - Output (Min/Fixed):
- -
- Voltage - Output (Max):
- -
- Current - Output:
- -
- Frequency - Switching:
- -
- Synchronous Rectifier:
- -
- Operating Temperature:
- -
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- -
- Supplier Device Package:
- -
MAX856CUA+ FAQ
1.How can I place an order for MAX856CUA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX856CUA+ 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 MAX856CUA+ reliable?
The price and inventory of MAX856CUA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX856CUA+ is usually 5 days.
3.What payment methods are accepted for MAX856CUA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX856CUA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX856CUA+?
MAX856CUA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX856CUA+ 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 MAX856CUA+?
For technical support, including MAX856CUA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX856CUA+ requirements.
6.How does Aetrix verify that MAX856CUA+ is sourced from the original manufacturer or authorized distributors?
All MAX856CUA+ 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 MAX856CUA+ meets industry standards.
7.What is the process for return or replacement of MAX856CUA+?
All MAX856CUA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX856CUA+, 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 MAX856CUA+ part is unused and in its original packaging.
Return procedure for MAX856CUA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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