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Analog Devices Inc./Maxim Integrated MAX1688ESA+T
- Part No.:
- MAX1688ESA+T
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
MAX1688ESA+T.pdf
- Description:
- IC REG BOOST ADJ 730MA 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,937
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Product details
Overview
MAX1688ESA+T 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 to 6V adjustable output, 2.7V–6V input range, and 90% peak efficiency. It operates in 8-pin SO package with internal synchronous rectification and logic-controlled shutdown.
For engineers reviewing the MAX1688ESA+T datasheet, MAX1688ESA+T pinout, MAX1688ESA+T application, or MAX1688ESA+T equivalent, key selection criteria include its GSM-specific adaptive recharge algorithm, 3µA shutdown current, precise 1.25V feedback reference, and compatibility with Li-Ion/NiMH battery inputs requiring low surge current and minimal voltage sag.
Technical Context
The MAX1688ESA+T implements hysteretic inductor-current control with programmable peak current via CHG pin, enabling self-regulating reservoir capacitor recharge time that compensates for VOUT droop and input voltage variation. Its functional diagram integrates dual MOSFETs (P-channel and N-channel), internal current-sense resistor, and analog feedback loop referenced to 1.25V FB threshold.
It supports synchronized standby mode triggered by ON pin low assertion (>1.2ms for shutdown), disconnecting output from input during RF transmit bursts to eliminate switching noise and reduce battery surge. Startup employs four-phase sequencing (Linear → Pseudo Buck → Pseudo Boost → Boost) to limit inrush current.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Voltage Range | 1.25V to 6V - set externally via resistor divider on FB pin; enables flexible rail generation for RF PA biasing. |
| Input Voltage Range | 2.7V to 6V - supports single Li-Ion (2.7–4.2V), three NiMH (3.0–4.5V), or alkaline cells without external regulation. |
| Peak Efficiency | 90% - achieved using internal synchronous rectifier, eliminating Schottky diode loss and reducing thermal load. |
| Shutdown Current | 3µA - ensures ultra-low quiescent draw during RF transmit intervals, extending battery runtime in burst-mode systems. |
| Feedback Reference | 1.25V ±3% - high-precision internal reference enables accurate output regulation across temperature and load conditions. |
| Switching Frequency | Exceeds 1MHz - determined by inductor value and load; allows compact magnetics and reduced EMI filtering requirements. |
| Operating Temperature | –40°C to +85°C - qualified for industrial and mobile handset environments with full parameter guarantee. |
Pinout & Package
MAX1688ESA+T is housed in an 8-pin SO (Small Outline) package, 1.75mm body width, with gull-wing leads and JEDEC MS-012AC standard footprint. Thermal performance supports 471mW continuous dissipation at +70°C ambient.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 IN | Supply Input | Battery input connection; requires ≥47µF bypass capacitor to PGND for stability and transient response. |
| 2 LX1 | Internal N-Channel Drain | Connects to inductor high-side; carries pulsed switch current and must be routed with low-inductance path. |
| 3 FB | Feedback Input | Regulates output by comparing divided VOUT to 1.25V reference; sets output voltage via R1/R2 divider. |
| 4 LX2 | Internal P-Channel Drain | Connects to inductor low-side and PGND; forms synchronous rectifier node with LX1. |
| 5 ON | Logic Control Input | Active-high enable; low >1.2ms forces shutdown (3µA IQ); synchronizes standby during RF bursts. |
| 6 CHG | Constant-Recharge-Time Set | Resistor-to-GND sets adaptive recharge time; determines peak inductor current based on VOUT droop. |
| 7 REF | Reference Output | 1.25V buffered reference; supplies up to 10µA for external LIM divider or DAC biasing (TSSOP only). |
| 8 GND | Ground Return | Analog and power ground tie point; requires star grounding with PGND and AGND pins tied at single point. |
Key Features
| Feature | Design Value |
|---|---|
| Adaptive Constant-Recharge-Time Algorithm | Self-adjusts peak inductor current based on measured VOUT sag, maintaining fixed recharge duration across varying battery voltage and capacitor ESR. |
| Internal Synchronous Rectification | Eliminates external Schottky diode, reducing conduction loss and PCB area while improving efficiency above 90%. |
| Four-Phase Soft-Start Sequence | Prevents inrush current via Linear → Pseudo Buck → Pseudo Boost → Boost transitions, limiting battery stress at power-up. |
| Output Disconnect in Shutdown | Isolates VOUT from VIN during shutdown, preventing reverse current flow and protecting downstream circuitry. |
| GSM Burst-Optimized Standby Mode | ON pin synchronization halts switching during RF transmit, sourcing burst load from reservoir capacitor without noise coupling. |
Applications
| GSM Mobile Handsets | Wireless LAN Transceivers |
|---|---|
Use Scenario: Powering RF power amplifiers during 12% duty-cycle GSM transmit bursts with 2.66A peak current demand. IC Role / Device Role / Timing Role: Step-up DC-DC converter providing regulated 5V output from declining Li-Ion battery, entering standby synchronized to TX enable signal. Use Value: Limits peak battery current to ≤450mA, reduces voltage sag below 100mV, and extends usable battery life by minimizing surge-induced capacity loss. | Use Scenario: Supplying 3.3V/500mA burst loads in 802.11b/g WLAN PCMCIA cards operating from 3-cell NiMH packs. IC Role / Device Role / Timing Role: High-efficiency boost regulator with adaptive recharge, dynamically adjusting peak current to maintain stable output under variable packet-length bursts. Use Value: Enables compact design with 10µH inductor and 2000µF reservoir capacitor, achieving >85% efficiency at 300mA average load and <200mV ripple. |
| PC Card (PCMCIA) Power Management | Low-Power Industrial Telemetry Modules |
Use Scenario: Delivering regulated 3.3V to PC card peripherals with strict 1A input current limit enforced by host socket specifications. IC Role / Device Role / Timing Role: Adjustable-current-limit boost converter using LIM pin (for MAX1687) or CHG pin (for MAX1688) to comply with PCMCIA Class A/B current profiles. Use Value: Meets PCMCIA 2.1 specification for hot-plug current ramp rate and steady-state limits without external current-sense circuitry. | Use Scenario: Powering narrowband IoT transmitters (e.g., LoRa, NB-IoT) requiring 3.6V/150mA bursts every 10 seconds from primary alkaline cells. IC Role / Device Role / Timing Role: Battery-efficient boost converter leveraging adaptive recharge to minimize average input current while sustaining 300ms burst capability. Use Value: Achieves >7-year battery life on two AA cells by limiting average input current to <100µA between transmissions and eliminating unnecessary switching. |
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 | Uses voltage-controlled current limit (LIM pin) instead of adaptive CHG-based recharge; lacks self-regulating droop compensation. | Suitable for fixed-burst or microcontroller-controlled current limiting; less optimal for varying battery voltage or capacitor aging. | Select MAX1687ESA when precise programmable current limit is required over adaptive recharge behavior. |
| TPS61040DRVR | Fixed 500kHz switching frequency, no adaptive recharge, 0.5A max output current, 2.5V–6V input, 1.25V reference. | Targeted at general-purpose boost applications; lacks GSM-specific standby synchronization and reservoir capacitor management logic. | Choose TPS61040DRVR for cost-sensitive non-GSM designs where 500kHz operation and simpler control suffice. |
Compared with MAX1687ESA and TPS61040DRVR, the MAX1688ESA+T uniquely delivers adaptive recharge timing that maintains consistent reservoir recovery across battery discharge and component tolerance, making it the only option among the three qualified for GSM-compliant RF PA supply with minimal voltage sag and noise.
Availability
MAX1688ESA+T is available at Aetrix Electronics and suitable for GSM handsets, wireless LAN modules, PCMCIA power management, and industrial telemetry systems requiring stable component supply with guaranteed long-term availability and traceable sourcing.
Supply support for MAX1688ESA+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 communications, computing, and industrial markets.
The MAX1687/MAX1688 product line was engineered specifically for GSM and burst-load RF power amplifier supply, emphasizing low battery surge current, adaptive reservoir capacitor recharge, and noise-free operation during critical transmit windows.
FAQ
What is the function of the CHG pin on the MAX1688ESA+T?
The CHG pin on the MAX1688ESA+T sets the adaptive constant-recharge-time behavior by connecting an external resistor to GND. This resistor determines how aggressively the device recharges the output reservoir capacitor after each RF burst, directly controlling peak inductor current to compensate for VOUT droop and input voltage variation. Unlike the MAX1687ESA's LIM pin, CHG enables self-regulation without microcontroller intervention.
Does the MAX1688ESA+T require an external Schottky diode?
No, the MAX1688ESA+T does not require an external Schottky diode because it integrates synchronous rectification using internal P-channel and N-channel MOSFETs. This architecture eliminates forward-voltage drop losses, improves conversion efficiency to over 90%, reduces thermal dissipation, and simplifies PCB layout by removing the need for an external diode and its associated footprint and routing constraints.
How does the MAX1688ESA+T minimize battery voltage sag during GSM bursts?
The MAX1688ESA+T minimizes battery voltage sag by charging a large output reservoir capacitor during system idle time, then supplying the entire RF burst load from that capacitor while the converter enters standby mode. Its adaptive recharge algorithm ensures the capacitor is replenished in a fixed time regardless of battery voltage or capacitor ESR, limiting peak battery current to ≤450mA and holding VBAT sag below 100mV even at end-of-discharge.
Can the MAX1688ESA+T operate with a single alkaline cell?
Yes, the MAX1688ESA+T supports input voltages from 2.7V to 6V, making it compatible with three alkaline cells (nominal 4.5V, range ~3.0–4.8V). A single alkaline cell (1.5V) falls below the 2.7V minimum input requirement and cannot power the MAX1688ESA+T directly; two alkaline cells (3.0V minimum) meet the spec and are commonly used in low-power telemetry applications with this IC.
What is the purpose of the four-phase startup sequence in the MAX1688ESA+T?
The four-phase startup sequence (Linear Regulator → Pseudo Buck → Pseudo Boost → Boost) in the MAX1688ESA+T controls inrush current during initial power-up by gradually ramping output voltage while limiting battery current. This prevents excessive voltage droop that could reset other system components, ensures reliable start-up across weak or aged batteries, and avoids triggering undervoltage lockout in companion ICs sharing the same battery rail.
MAX1688ESA+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:
- 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+T FAQ
1.How can I place an order for MAX1688ESA+T through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1688ESA+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 MAX1688ESA+T reliable?
The price and inventory of MAX1688ESA+T are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1688ESA+T is usually 5 days.
3.What payment methods are accepted for MAX1688ESA+T?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1688ESA+T transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1688ESA+T?
MAX1688ESA+T orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1688ESA+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 MAX1688ESA+T?
For technical support, including MAX1688ESA+T datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1688ESA+T requirements.
6.How does Aetrix verify that MAX1688ESA+T is sourced from the original manufacturer or authorized distributors?
All MAX1688ESA+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 MAX1688ESA+T meets industry standards.
7.What is the process for return or replacement of MAX1688ESA+T?
All MAX1688ESA+T units undergo pre-shipment inspection (PSI). If there is an issue with MAX1688ESA+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 MAX1688ESA+T part is unused and in its original packaging.
Return procedure for MAX1688ESA+T:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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