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Analog Devices Inc./Maxim Integrated MAX1688ESA+
- Part No.:
- MAX1688ESA+
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX1688ESA+.pdf
- Description:
- IC REG BOOST ADJ 730MA 8SOIC
- Quantity:
- Payment:
- Shipping:
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Product details
Overview
MAX1688ESA+ from Maxim Integrated is a step-up DC-DC converter IC designed for GSM RF power amplifier burst-load supply, featuring adaptive constant-recharge-time current limiting, 1.25V–6V adjustable output, 2.7V–6V input range, and 90% peak efficiency. It operates in 8-pin SO package and delivers up to 2W while limiting peak battery current to 450mA for Li-Ion/NiMH-powered handsets.
For engineers reviewing the MAX1688ESA+ datasheet, MAX1688ESA+ pinout, MAX1688ESA+ application, or MAX1688ESA+ equivalent, key selection criteria include its GSM-synchronized standby mode, CHG-pin-controlled recharge timing, internal synchronous rectification, 3µA shutdown current, and precise 1.25V feedback reference with ±2% tolerance over –40°C to +85°C.
Technical Context
The MAX1688ESA+ implements hysteretic inductor-current control with peak current set by the CHG pin voltage and internal transconductance (gmCHG = 0.8A/V), enabling adaptive recharge of the output reservoir capacitor based on VOUT droop. Its functional diagram integrates dual MOSFETs (P-channel and N-channel), internal current-sense resistor (RSENSE = 0.7Ω typ), and analog ground (AGND) / power ground (PGND) separation for noise-sensitive RF burst operation.
It supports four-phase startup (Linear Regulator → Pseudo Buck → Pseudo Boost → Boost) to limit inrush current, and enters standby mode on ON pin low assertion-disconnecting output from input and ramping inductor current to zero-then shuts down after 1.2ms with 3µA quiescent current. The CHG pin sets fixed recharge time via external resistor (e.g., 40.2kΩ for optimized GSM recovery).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 2.7V to 6V - supports single Li-Ion, three NiMH, or three alkaline cells without external regulation. |
| Output Voltage Range | 1.25V to 6V - set externally via resistor divider on FB pin; 1.25V nominal feedback threshold enables precise regulation. |
| Peak Efficiency | 90% - achieved using internal synchronous rectification, eliminating external Schottky diode and reducing conduction loss. |
| Shutdown Current | 3µA - enables ultra-low-power system sleep states; verified at VIN = 4.2V, VOUT = 0, ON = GND. |
| Operating Temperature | –40°C to +85°C - specified across full industrial range; FB set voltage drift ≤ ±2% over this range. |
| Switching Frequency | Exceeds 1MHz - determined by inductor value and load; typical 150kHz–1MHz range allows compact magnetics selection. |
| Peak Battery Current | 450mA - limits surge during GSM 12% duty-cycle bursts, extending battery life and minimizing voltage sag. |
Pinout & Package
MAX1688ESA+ is housed in an 8-pin SO (Small Outline) package, 1.75mm height, JEDEC MS-012AC compliant, with gull-wing leads and Pb-free + RoHS-compliant finish.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 IN | Supply Input | Battery input connection; requires ≥47µF bypass capacitor to PGND to stabilize input during high-current bursts. |
| 2 LX1 | Internal N-Channel Switch Source | Connects to inductor; forms low-side switch node with LX2; internal RSENSE (0.7Ω) senses current for adaptive control. |
| 3 FB | Feedback Input | Regulates output to 1.25V nominal; connects to resistor divider from OUT to GND; gmFB = 200µA/V ensures stable loop response. |
| 4 REF | Reference Output | 1.25V ±2% precision reference; supplies ≤10µA; used for LIM/CHG biasing in TSSOP variants (not used in SO package per pinout). |
| 5 AGND | Analog Ground | Separate ground return for FB, REF, and CHG/LIM circuitry to prevent noise coupling into regulation path. |
| 6 PGND | Power Ground | High-current return for LX1, LX2, and OUT; must be star-connected to minimize ground bounce during switching. |
| 7 ON | Logic Control Input | Active-high enable; low for >1.2ms triggers 3µA shutdown; synchronized low during RF transmit eliminates switching noise injection. |
| 8 CHG | Constant-Recharge-Time Input | Accepts external resistor to GND (e.g., 40.2kΩ); sets peak inductor current to achieve fixed recharge time after GSM burst. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive Constant-Recharge-Time Algorithm | Uses CHG pin and internal gmCHG to dynamically adjust peak inductor current based on VOUT droop-ensuring consistent reservoir capacitor recharge time across varying battery voltage and load conditions. |
| Internal Synchronous Rectification | Integrates P-channel and N-channel MOSFETs with RDS(ON) ≤0.8Ω (P) and ≤0.18Ω (N), eliminating external Schottky diode and improving efficiency by ~5% vs. asynchronous designs. |
| GSM-Synchronized Standby Mode | ON pin assertion disables switching during RF transmit bursts, allowing output reservoir capacitor to supply peak load current-removing switching noise from sensitive RF front-end circuits. |
| Four-Phase Soft-Start Sequence | Progresses from Linear Regulator → Pseudo Buck → Pseudo Boost → Boost to limit inrush current and prevent battery voltage collapse during power-up. |
| Output Disconnect During Shutdown | Internal switches isolate OUT from IN when ON = low, preventing reverse current flow and protecting downstream circuitry during battery removal or deep sleep. |
Applications
| GSM Mobile Handset Power Supply | Wireless LAN PC Card (PCMCIA) |
|---|---|
Use Scenario: Supplies 5V/2A pulsed power to RF power amplifier during 12% duty-cycle GSM transmit bursts from a single Li-Ion cell. IC Role / Device Role / Timing Role: Step-up DC-DC converter with adaptive recharge timing; synchronizes ON pin disable with RF transmit window to eliminate switching noise. Use Value: Limits peak battery current to 450mA, extends usable battery life by 18% vs. non-adaptive converters, and reduces voltage sag below 3.0V during burst. | Use Scenario: Powers 3.3V/350mA continuous load in PCMCIA wireless adapter operating from 2.7–6V host bus supply. IC Role / Device Role / Timing Role: Adjustable-output boost regulator with fixed-current-limit configuration; uses LIM pin tied to GND for 200mA limit in non-burst applications. Use Value: Delivers stable 3.3V output with <50mV ripple under full load, leveraging internal 0.7Ω sense resistor and 90% efficiency to minimize thermal rise in compact card form factor. |
| Industrial Telematics Module | Portable Medical Pulse Oximeter |
Use Scenario: Provides regulated 5.5V supply to cellular modem during intermittent data transmission bursts in vehicle-mounted tracking units. IC Role / Device Role / Timing Role: Burst-mode power manager; CHG pin configured for 31.5kΩ to match 2.66A IBURST and 0.36V VDROOP per GSM spec. Use Value: Achieves 1.2ms recovery time post-burst with <1% output droop, ensuring reliable modem handshake even at end-of-battery-life (2.7V VIN). | Use Scenario: Powers LED driver and analog front-end in battery-operated pulse oximeter requiring low-noise, low-EMI power delivery during optical sensing cycles. IC Role / Device Role / Timing Role: Low-EMI boost converter; ON pin controlled by microcontroller to disable switching during ADC sampling windows. Use Value: Reduces conducted EMI by >20dB in 1–10MHz band versus always-on converters, preserving signal integrity of weak photodiode current 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 |
|---|---|---|---|
| MAX1687ESA+ | Lacks CHG pin; uses LIM pin for fixed voltage-controlled current limit (0–1V input); no adaptive recharge algorithm. | Suitable for systems with predictable, fixed burst profiles where recharge timing need not adapt to battery voltage decay. | Select MAX1687ESA+ when microcontroller-based current limit adjustment is required and adaptive VOUT-droop response is unnecessary. |
| TPS61040DRVR | Fixed 500kHz switching frequency; no CHG/LIM pins; 0.5A max output; lacks GSM-specific standby synchronization logic. | Targeted at general-purpose portable electronics-not optimized for RF burst noise isolation or reservoir capacitor management. | Choose TPS61040DRVR only for cost-sensitive, non-GSM applications requiring basic boost functionality with minimal external components. |
Compared with MAX1687ESA+, the MAX1688ESA+ provides superior battery life extension via adaptive recharge timing, while TPS61040DRVR offers simpler layout but cannot replicate GSM-synchronized noise suppression or droop-compensated current control-making MAX1688ESA+ the only choice for RF-critical burst-load designs.
Availability
MAX1688ESA+ is available at Aetrix Electronics and suitable for GSM handset design, wireless PC card development, and industrial telematics modules requiring stable component supply with guaranteed long-term availability and full traceability.
Supply support for MAX1688ESA+ 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 demanding industrial, communications, and consumer applications.
The MAX1687/MAX1688 product line was engineered specifically for GSM/RF burst-load power management, addressing the need for low-noise, battery-preserving DC-DC conversion in space-constrained mobile handsets and wireless peripherals.
FAQ
What is the function of the CHG pin on the MAX1688ESA+?
The CHG pin on the MAX1688ESA+ sets the constant-recharge-time behavior by accepting an external resistor to GND. This resistor determines peak inductor current to ensure the output reservoir capacitor recharges fully within a fixed time after each GSM burst-compensating for battery voltage decay and capacitor aging. Unlike the MAX1687ESA+, the MAX1688ESA+ does not use the LIM pin; CHG is its defining adaptive control interface.
Does the MAX1688ESA+ require an external Schottky diode?
No, the MAX1688ESA+ does not require an external Schottky diode. It integrates internal synchronous rectification using complementary P-channel and N-channel MOSFETs, achieving >90% efficiency and eliminating diode forward-voltage loss and associated thermal stress. This integration reduces bill-of-materials count and PCB area versus asynchronous boost converters.
Can the MAX1688ESA+ operate with a 2.7V input and deliver 5V at 1A continuous load?
Yes, the MAX1688ESA+ supports 2.7V–6V input and can deliver 5V at 1A continuous load, though efficiency drops to ~75% at VIN = 2.7V per Typical Operating Characteristics. For GSM burst loads (e.g., 2A at 12% duty cycle), it sustains 5V output with <100mV droop using a 2000µF low-ESR output capacitor-verified in Figure 7 application circuit.
How does the MAX1688ESA+ reduce switching noise during RF transmission?
The MAX1688ESA+ reduces switching noise during RF transmission by synchronizing its ON pin to the RF transmit window: asserting ON = low places the IC in standby mode, halting switching and allowing the output reservoir capacitor to supply burst current. This eliminates high-frequency switching harmonics from coupling into the RF front-end-critical for meeting GSM spectral mask requirements.
What is the maximum recommended output capacitor value for the MAX1688ESA+?
The MAX1688ESA+ has no absolute maximum output capacitor value, but practical design limits apply: for GSM burst applications, 2000µF is standard (per Figure 7), and values up to 4700µF are supported with proper ESR (<10mΩ) and layout. Larger capacitors improve droop margin but increase inrush current and startup time-requiring verification of the four-phase soft-start sequence under worst-case conditions.
MAX1688ESA+ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Function:
- Step-Up
- Output Configuration:
- Positive
- Topology:
- Boost
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 2.7V
- Voltage - Input (Max):
- 6V
- Voltage - Output (Min/Fixed):
- 1.25V
- Voltage - Output (Max):
- 6V
- Current - Output:
- 730mA (Switch)
- Frequency - Switching:
- 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 8-SOIC
MAX1688ESA+ FAQ
1.How can I place an order for MAX1688ESA+ through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1688ESA+ 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 MAX1688ESA+ reliable?
The price and inventory of MAX1688ESA+ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1688ESA+ is usually 5 days.
3.What payment methods are accepted for MAX1688ESA+?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1688ESA+ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1688ESA+?
MAX1688ESA+ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1688ESA+ 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 MAX1688ESA+?
For technical support, including MAX1688ESA+ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1688ESA+ requirements.
6.How does Aetrix verify that MAX1688ESA+ is sourced from the original manufacturer or authorized distributors?
All MAX1688ESA+ 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 MAX1688ESA+ meets industry standards.
7.What is the process for return or replacement of MAX1688ESA+?
All MAX1688ESA+ units undergo pre-shipment inspection (PSI). If there is an issue with MAX1688ESA+, 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 MAX1688ESA+ part is unused and in its original packaging.
Return procedure for MAX1688ESA+:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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