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Analog Devices Inc./Maxim Integrated MAX859CUA+
- Part No.:
- MAX859CUA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Datasheet:
-
MAX859CUA+.pdf
- Description:
- IC REG BOOST ADJ 125MA 8UMAX
- Quantity:
- Payment:
- Shipping:
Inventory:1,399
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Product details
Overview
The MAX859CUA+ from Maxim Integrated is an adjustable-output, step-up DC-DC switching regulator optimized for low-input-voltage battery-powered systems. It accepts 0.8V–6.0V input and delivers 2.7V–6.0V output with 125mA peak switch current limit, ±1.5% reference tolerance, and 25µA quiescent supply current - enabling extended runtime in glucose meters and portable medical instrumentation.
For engineers reviewing the MAX859CUA+ datasheet, MAX859CUA+ pinout, MAX859CUA+ application, or MAX859CUA+ equivalent, this page provides verified technical context, validated pin functions, confirmed efficiency curves at 3.3V/5V loads, real-world low-battery detection implementation guidance, and two rigorously cross-checked alternative parts for adjustable-output boost conversion.
Technical Context
The MAX859CUA+ uses a minimum-off-time, current-limited pulse-frequency modulation (PFM) control scheme with no oscillator - switching frequency varies from near-zero to 500kHz depending on load and input voltage. Its internal N-channel sense-FET has ~4Ω on-resistance and 125mA ±25mA fixed peak current limit, enabling compact 47µH inductor use without external current-sense circuitry.
It integrates a precision 1.25V reference (±1.5% over temperature), open-drain low-battery detector (LBI/LBO) with 1.25V threshold and 25mV hysteresis, and bootstrapped operation powered from OUT. The FB pin accepts external resistor dividers for output voltage setting, while SHDN enables 1µA shutdown mode with no reverse-battery protection.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 0.8V to 6.0V - supports single-cell alkaline, NiMH, or LiFePO₄ batteries down to 0.8V post-startup. |
| Output Voltage Range | 2.7V to 6.0V - set via external FB resistor divider; not factory-trimmed but referenced to 1.25V ±1.5%. |
| Peak Switch Current Limit | 125mA ±25mA - defines maximum inductor current; enables use of low-cost, small-footprint 47µH inductors. |
| Quiescent Supply Current | 25µA - measured at 3.3V output; directly correlates to battery drain in always-on portable devices. |
| Shutdown Current | 1µA - ensures negligible battery leakage during system sleep; specified across full temperature range. |
| Reference Voltage | 1.25V ±1.5% over -40°C to +85°C - stable enough to drive ADC references or external comparators without buffering. |
| Switching Frequency | Up to 500kHz - variable PFM operation reduces EMI vs. fixed-frequency PWM; no external clock required. |
Pinout & Package
MAX859CUA+ is housed in an 8-pin µMAX package (3.0mm × 3.0mm, 0.8mm height), pin-compatible with SO-8 but with 0.65mm lead pitch and exposed pad for thermal enhancement. The package meets JEDEC MO-187AC standards and is rated for 0°C to +70°C operation.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| LX | N-channel MOSFET drain | Switch node connecting to inductor; requires short, low-inductance PCB trace to minimize ringing and EMI. |
| GND | Power ground | Must be soldered directly to solid ground plane; shared return for LX, OUT, REF, FB, LBI, LBO, SHDN. |
| OUT | Regulator output & bootstrap supply | Provides power to internal circuitry; connects to output capacitor and Schottky anode; not regulated by feedback loop. |
| LBI | Low-battery input | High-impedance comparator input (≤100nA bias); threshold = 1.25V; connect to voltage divider from VIN for battery monitoring. |
| LBO | Low-battery open-drain output | Sinks current when LBI < 1.25V; requires external pull-up (≥10kΩ to OUT) for CMOS logic interface. |
| REF | 1.25V precision reference output | Capable of sourcing 250µA / sinking 20µA; bypass with 0.22µF ceramic to GND if loaded. |
| FB | Feedback input | Connects to resistor divider between OUT and GND; sets output voltage per VOUT = 1.25V × (1 + R1/R2). |
| SHDN | Active-low shutdown control | Logic-level input (0.4V low / 1.6V high); pulls internal circuitry into 1µA state; unclamped - tolerates up to 7V. |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low quiescent current | 25µA operating / 1µA shutdown - extends battery life in intermittent-use medical devices like glucose meters. |
| Adjustable output via FB pin | Supports 2.7V–6.0V output with standard 1% resistors; eliminates need for multiple fixed-output SKUs in BOM. |
| Integrated low-battery detector | On-chip comparator with 1.25V threshold and 25mV hysteresis - removes external supervisor IC in space-constrained designs. |
| Internal 125mA current-limited switch | Enables use of low-cost, miniature 47µH inductors (e.g., Sumida CDR74B-470) without saturation risk at full load. |
| Bootstrapped operation | Derives internal supply from OUT pin - allows startup from 0.8V input and operation down to 0.8V battery sag after startup. |
Applications
| Glucose Meters | Portable Data Collectors |
|---|---|
Use Scenario: Battery-powered handheld device measuring blood glucose concentration with LCD display and microcontroller. IC Role / Device Role / Timing Role: Step-up converter generating stable 3.3V rail from single 1.5V alkaline cell for MCU, sensor interface, and display driver. Use Value: 25µA quiescent current minimizes standby drain; 125mA peak limit supports pulsed LED backlight and sensor excitation without oversized inductor. |
Use Scenario: Ruggedized field instrument capturing barcodes, RFID, or environmental sensor data on 2-cell NiMH battery. IC Role / Device Role / Timing Role: Adjustable boost regulator delivering 5.0V to USB-UART bridge and 3.3V to microcontroller via dual-output configuration. Use Value: FB-based adjustability allows single BOM part to support multiple voltage rails; LBO signal triggers low-power alert before battery exhaustion. |
| Personal Data Communicators | Medical Instrumentation |
Use Scenario: Palm-sized PDA with monochrome LCD, IR transceiver, and flash memory, powered by 2×AA cells. IC Role / Device Role / Timing Role: Primary power supply converting 1.8V–3.0V battery range to regulated 3.3V system rail with dynamic load handling. Use Value: PFM control maintains >85% efficiency from 1mA to 25mA load - critical for long idle periods between user interactions. |
Use Scenario: Portable ECG monitor using analog front-end, ADC, and Bluetooth LE radio, operating from coin-cell or AAA battery. IC Role / Device Role / Timing Role: High-efficiency boost stage powering precision analog circuitry and digital subsystems from ultra-low input voltages. Use Value: 1.25V reference accuracy (±1.5%) enables direct ADC reference use; REF pin sourcing capability eliminates external buffer. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar adjustable-output boost converter applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS61200DRCR | Fixed 500kHz PWM; 1.8V min start-up; 600mA switch current; integrated sync rectifier. | Higher output current but higher quiescent current (55µA); requires external compensation for adjustable output. | Prefer TPS61200DRCR when >100mA continuous load or synchronous rectification is needed; avoid if <25µA quiescent is mandatory. |
| LT1944EMS8-1 | PFM/PWM hybrid; 1.8V min start-up; 600mA switch; built-in soft-start; ±2% reference. | Wider input range (1.8V–10V); higher quiescent current (110µA); larger SO-8 footprint. | Choose LT1944EMS8-1 for multi-cell battery inputs or where soft-start prevents inrush; not suitable for sub-1V startup or ultra-low IQ. |
Compared with MAX859CUA+, both alternatives offer higher output current but significantly higher quiescent current - making them unsuitable for glucose meters or other sub-25µA standby-critical applications. Only MAX859CUA+ guarantees reliable 0.8V startup and 1µA shutdown in the µMAX package.
Availability
MAX859CUA+ is available at Aetrix Electronics and suitable for glucose meters, portable medical instrumentation, personal data communicators, and 2-cell battery-operated equipment requiring stable component supply with guaranteed long-term lifecycle support.
Supply support for MAX859CUA+ 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, medical, and portable applications.
The MAX856–MAX859 family was designed specifically for ultra-low-power, single-cell battery-powered systems requiring high-efficiency step-up conversion with integrated low-battery monitoring - targeting medical, handheld, and IoT edge devices.
FAQ
What is the minimum input voltage required to start up the MAX859CUA+?
The MAX859CUA+ has a typical start-up input voltage of 0.8V, verified across load conditions up to 25mA. This is enabled by its low-threshold N-channel sense-FET and bootstrapped architecture. At 0mA load, startup occurs at 0.8V; at 25mA load, it rises to 1.0V - values confirmed in Figure MAX856-07 of the official datasheet. The MAX859CUA+ maintains regulation down to 0.8V after startup.
Can the MAX859CUA+ be used to generate 3.3V from a 1.5V alkaline cell?
Yes - the MAX859CUA+ is explicitly validated for this use case. With a 1.5V input, it delivers 3.3V at up to 25mA with >85% efficiency (per Figure MAX856-01). Its 0.8V startup capability ensures operation even as the alkaline cell discharges below 1.0V. External components required are a 47µH inductor, 1N5817 Schottky diode, and 22µF output capacitor - all specified in the MAX859CUA+ typical application circuit.
How does the low-battery detection function work on the MAX859CUA+?
The MAX859CUA+ implements low-battery detection using the LBI and LBO pins: LBI is a high-impedance input referenced to the internal 1.25V bandgap; when voltage at LBI falls below 1.25V (±25mV hysteresis), LBO - an open-drain N-channel MOSFET - sinks current to GND. To configure, connect LBI to a resistor divider from VIN; LBO requires a ≥10kΩ pull-up to OUT. This function is fully integrated - no external comparator or reference needed.
What is the purpose of the REF pin on the MAX859CUA+ and how should it be bypassed?
REF provides a buffered 1.25V ±1.5% reference output capable of sourcing 250µA or sinking 20µA - usable for ADC references, comparator thresholds, or sensor biasing. When driving an external load, bypass REF to GND with a 0.22µF ceramic capacitor; if unloaded, ≥0.1µF suffices. This bypass stabilizes the reference under dynamic load and suppresses noise coupling into sensitive analog circuits powered by the MAX859CUA+.
Is the MAX859CUA+ pin-compatible with the MAX857CUA+?
No - MAX859CUA+ and MAX857CUA+ share the same 8-pin µMAX package and pinout (LX, GND, OUT, LBI, LBO, REF, FB, SHDN), but differ in internal functionality: MAX857CUA+ is a 500mA peak-current variant with different current-limiting architecture and higher efficiency at >50mA loads. While physically interchangeable, substituting MAX859CUA+ for MAX857CUA+ will reduce max output current from 100mA to 25mA and increase output ripple under heavy load.
MAX859CUA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 0.8V
- Voltage - Input (Max):
- 6V
- Voltage - Output (Min/Fixed):
- 2.7V
- Voltage - Output (Max):
- 6V
- Current - Output:
- 125mA (Switch)
- Frequency - Switching:
- 500kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- 0°C ~ 70°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-uMAX/uSOP
MAX859CUA+ FAQ
1.How can I place an order for MAX859CUA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX859CUA+ 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 MAX859CUA+ reliable?
The price and inventory of MAX859CUA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX859CUA+ is usually 5 days.
3.What payment methods are accepted for MAX859CUA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX859CUA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX859CUA+?
MAX859CUA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX859CUA+ 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 MAX859CUA+?
For technical support, including MAX859CUA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX859CUA+ requirements.
6.How does Aetrix verify that MAX859CUA+ is sourced from the original manufacturer or authorized distributors?
All MAX859CUA+ 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 MAX859CUA+ meets industry standards.
7.What is the process for return or replacement of MAX859CUA+?
All MAX859CUA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX859CUA+, 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 MAX859CUA+ part is unused and in its original packaging.
Return procedure for MAX859CUA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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