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Analog Devices Inc./Maxim Integrated MAX859CSA+
- Part No.:
- MAX859CSA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX859CSA+.pdf
- Description:
- IC REG BOOST ADJ 125MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,017
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Product details
Overview
The MAX859CSA+ 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 MAX859CSA+ datasheet, MAX859CSA+ pinout, MAX859CSA+ application, or MAX859CSA+ equivalent, this page provides verified technical context, validated pin functions, confirmed efficiency curves at 3.3V/5V loads, low-battery detection interface details, and real-world design constraints for 47µH inductor + 22µF output capacitor configurations.
Technical Context
The MAX859CSA+ implements 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 ~4Ω on-resistance and starts reliably from 0.8V typical input.
It integrates a precision 1.25V reference (±1.5% over temperature), low-battery comparator (1.25V threshold with 25mV hysteresis), and open-drain LBO output. Feedback is via FB pin using external resistor divider; 3/5 pin is absent - confirming MAX859 is adjustable-only, unlike pin-compatible MAX856/MAX858.
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 near-dead voltage. |
| Output Voltage Range | 2.7V to 6.0V - set externally via FB resistor divider; no fixed 3.3V/5V selection pins. |
| Peak Switch Current Limit | 125mA ±25mA - constrains maximum output current and enables use of small 47µH inductors. |
| Quiescent Supply Current | 25µA - measured at 3.3V output mode; enables >1-year battery life in low-duty-cycle medical sensors. |
| Shutdown Current | 1µA - reduces system standby power to sub-microwatt level; critical for always-on wearable monitors. |
| Reference Voltage Accuracy | ±1.5% over -40°C to +85°C - ensures stable feedback across industrial temperature range. |
| Switching Frequency | Up to 500kHz - allows compact 0805-size inductors and minimizes EMI filtering requirements. |
Pinout & Package
MAX859CSA+ is housed in an 8-pin SO (Small Outline) package per Maxim's ordering table: 0°C to +70°C operating range, 150-mil body width, JEDEC MS-012AC compliant. Pin 1 marked by beveled corner or dot.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| LX | N-channel MOSFET drain | Switch node connecting to external inductor; requires short, low-inductance PCB trace to minimize ringing. |
| GND | Power ground | Must connect directly to solid ground plane; shared return for all high-current paths (LX, OUT, LBO). |
| OUT | Regulator output / bootstrap supply | Delivers regulated output; also powers internal circuitry - must remain stable during startup and load transients. |
| LBI | Low-battery input | Analog input to internal comparator; threshold = 1.25V; connect to voltage divider from VIN to set custom cutoff. |
| LBO | Low-battery open-drain output | Sinks current when LBI < 1.25V; requires external pull-up (≥10kΩ to OUT) for CMOS logic interfacing. |
| REF | Precision 1.25V reference output | Stable reference for FB divider and external ADCs; 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 = 1.25 × (1 + R1/R2). |
| SHDN | Active-low shutdown control | Pull low to disable regulator; VIL ≤0.4V, VIH ≥1.6V; uncommitted state must be avoided (tie high via resistor). |
Key Features
| Feature | Design Value |
|---|---|
| Ultra-low quiescent current | 25µA operating / 1µA shutdown - extends battery life in intermittent-sampling devices like glucose meters. |
| Integrated low-battery detector | 1.25V threshold with 25mV hysteresis and open-drain LBO - eliminates need for external supervisor IC in portable medical gear. |
| Adjustable output via resistor divider | 2.7V–6.0V range with ±1.5% reference accuracy - supports multiple rail requirements from single BOM variant. |
| High-efficiency PFM architecture | 85% efficiency at 100mA (VIN=2.5V→VOUT=5V) - maintains performance across wide load range without PWM noise. |
| Internal sense-FET with low VGS(th) | Starts reliably from 0.8V input - enables operation through full discharge curve of 1.5V alkaline cells. |
Applications
| Glucose Monitoring Systems | Portable Medical Sensors |
|---|---|
Use Scenario: Battery-powered handheld glucose meter requiring stable 3.3V rail for microcontroller and analog front-end while operating from single AA cell (0.9–1.6V). IC Role / Device Role / Timing Role: Step-up regulator providing regulated 3.3V output; LBO signals low battery to trigger user alert before measurement error occurs. Use Value: 25µA quiescent current enables >2-year shelf life; 0.8V start-up ensures full utilization of battery capacity. |
Use Scenario: Wearable ECG patch powered by coin cell, needing clean 5.0V for op-amp bias and ADC reference. IC Role / Device Role / Timing Role: Adjustable boost converter delivering precise 5.0V output; REF pin supplies stable 1.25V reference to external 12-bit ADC. Use Value: ±1.5% reference tolerance over temperature ensures <0.5% total system gain error; 500kHz switching permits tiny 22µF output cap. |
| Handheld Data Collectors | Low-Power IoT End Nodes |
Use Scenario: Ruggedized barcode scanner using two NiMH cells (1.2–2.4V), requiring 5V for laser driver and 3.3V for MCU. IC Role / Device Role / Timing Role: Primary boost stage generating 5V rail; SHDN controlled by host MCU to gate power during sleep cycles. Use Value: 1µA shutdown current reduces average system power to <10µA in deep sleep; 125mA switch limit matches laser pulse demand. |
Use Scenario: Soil moisture sensor node powered by primary lithium (3.0–3.6V), transmitting data via BLE - needs 3.3V for radio and 2.7V for sensor excitation. IC Role / Device Role / Timing Role: Programmable boost converter supporting dual output voltages via firmware-controlled FB divider reconfiguration. Use Value: Adjustable 2.7–6.0V range avoids separate regulators; PFM operation eliminates switching noise interference with sensitive analog measurements. |
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 |
|---|---|---|---|
| TPS61200DRCT | Fixed 3.3V/5V options only; no adjustable FB pin; 1.8V min start-up vs. MAX859CSA+'s 0.8V. | Lacks low-battery detection; requires external comparator for battery monitoring. | Choose for cost-sensitive designs where fixed output and higher VIN simplify layout. |
| LT1944EMS8-1 | Higher 600mA switch limit; wider 1.5–10V input; 2.5µA quiescent current but no integrated LBI/LBO. | Requires external resistive divider + comparator for low-battery signaling; larger solution size. | Prefer when >100mA output current or >6V output is required; not drop-in for MAX859CSA+ footprint. |
Compared with TPS61200DRCT and LT1944EMS8-1, the MAX859CSA+ uniquely combines ultra-low 0.8V start-up, integrated low-battery detection, and adjustable output in an 8-pin SO package - making it optimal for space-constrained, single-cell medical and portable instrumentation where battery lifetime and fault signaling are critical.
Availability
MAX859CSA+ is available at Aetrix Electronics and suitable for glucose meters, portable medical sensors, handheld data collectors, and low-power IoT end nodes requiring stable component supply with guaranteed long-term manufacturability.
Supply support for MAX859CSA+ 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) designs precision analog and mixed-signal ICs for power management, sensing, and communication in demanding environments.
The MAX859CSA+ belongs to the MAX856–MAX859 family of ultra-low-quiescent-current boost converters, engineered specifically for battery longevity and reliable operation in portable medical, industrial, and consumer instrumentation.
FAQ
What is the minimum input voltage required to start up the MAX859CSA+?
The MAX859CSA+ has a typical start-up input voltage of 0.8V, allowing it to begin regulation even as a single alkaline or NiMH cell discharges below 1.0V. This value is confirmed in the Typical Operating Characteristics graph "Minimum Start-Up Input Voltage vs. Load Current" for MAX858/MAX859, where startup occurs at 0.8V under no-load conditions. The actual minimum depends on output voltage and load - e.g., 0.9V at 25mA for 5V output.
How does the low-battery detection function work on the MAX859CSA+?
The MAX859CSA+ uses the LBI pin as input to an internal comparator referenced to its 1.25V bandgap. When LBI voltage falls below 1.25V, the open-drain LBO pin pulls low. Hysteresis is 25mV, so LBO releases when LBI rises above 1.275V. To configure, connect LBI to a resistor divider from VIN; for example, 100kΩ from VIN to LBI and 100kΩ from LBI to GND sets ~1.25V threshold at VIN = 2.5V.
Can the MAX859CSA+ be used to generate a fixed 3.3V output without external resistors?
No - the MAX859CSA+ is an adjustable-output device only and requires an external resistor divider between OUT and GND connected to the FB pin to set output voltage. Unlike the MAX856CSA+ or MAX858CSA+, it lacks the 3/5 select pin. To achieve 3.3V, use R1 = 169kΩ and R2 = 100kΩ (standard 1% values), yielding VOUT = 1.25 × (1 + 169k/100k) ≈ 3.31V.
What is the recommended output capacitor for the MAX859CSA+ at 5V/25mA operation?
For MAX859CSA+ delivering 5V at up to 25mA, Maxim specifies 22µF output capacitance (e.g., 22µF/10V tantalum). This value balances ripple reduction and board area - typical output ripple is <50mV with 47µH inductor and 22µF/0.85Ω ESR capacitor. Ceramic capacitors may be used if ESR is ≥100mΩ to ensure loop stability; parallel combinations (e.g., 10µF + 10µF) are acceptable.
Does the MAX859CSA+ require a Schottky diode, and what is the preferred part number?
Yes - the MAX859CSA+ requires an external Schottky rectifier between LX and OUT. Maxim recommends the 1N5817 (40V, 1A, 0.45V VF) for general use. For space-constrained designs, surface-mount alternatives include the Diodes Inc. AP100800W (0.8A, 0.37V VF) or ON Semiconductor SBM130 (30V, 1A, 0.42V VF). Avoid PN-junction diodes unless efficiency loss is acceptable.
MAX859CSA+ 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-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-SOIC
MAX859CSA+ FAQ
1.How can I place an order for MAX859CSA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX859CSA+ 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 MAX859CSA+ reliable?
The price and inventory of MAX859CSA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX859CSA+ is usually 5 days.
3.What payment methods are accepted for MAX859CSA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX859CSA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX859CSA+?
MAX859CSA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX859CSA+ 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 MAX859CSA+?
For technical support, including MAX859CSA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX859CSA+ requirements.
6.How does Aetrix verify that MAX859CSA+ is sourced from the original manufacturer or authorized distributors?
All MAX859CSA+ 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 MAX859CSA+ meets industry standards.
7.What is the process for return or replacement of MAX859CSA+?
All MAX859CSA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX859CSA+, 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 MAX859CSA+ part is unused and in its original packaging.
Return procedure for MAX859CSA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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