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Analog Devices Inc./Maxim Integrated MAX1977EEI
- Part No.:
- MAX1977EEI
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Special Purpose Regulators
- Package:
- 28-SSOP (0.154", 3.90mm Width)
- Datasheet:
-
MAX1977EEI.pdf
- Description:
- IC REG LINEAR MAIN PWR SUP CNTLR
- Quantity:
- Payment:
- Shipping:
Inventory:225
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Product details
Overview
MAX1977EEI from Maxim Integrated is a dual step-down switch-mode power-supply (SMPS) controller with integrated 5V/3.3V linear regulators, designed for notebook main power supplies. It delivers fixed 400kHz/500kHz switching frequencies, supports 4.5V–24V input, provides ±1.5% output voltage accuracy, and operates across –40°C to +85°C in a 28-pin QSOP package for battery-powered computing systems.
For engineers reviewing the MAX1977EEI datasheet, MAX1977EEI pinout, MAX1977EEI application, or MAX1977EEI equivalent, this page details its Quick-PWM™ transient response (100ns), ultrasonic pulse-skipping mode (>25kHz), dual-mode feedback (fixed/adjustable), PGOOD signaling, and bootstrapped LDO regulation - all critical for low-noise, high-efficiency portable power design.
Technical Context
The MAX1977EEI implements Maxim's proprietary Quick-PWM™ constant-on-time control without external current-sense resistors, enabling 100ns load-step response while maintaining stable frequency. Its dual PWM controllers operate at 400kHz (5V rail) and 500kHz (3.3V rail), optimized for thin-and-light applications.
It integrates two 100mA linear regulators (LDO5/LDO3) with automatic bootstrapping from SMPS outputs, internal soft-start/soft-stop discharge, and programmable fault protection via PRO, SKIP, and TON pins. The device uses separate current-limit inputs (ILIM3/ILIM5) and feedback paths (FB3/FB5) for independent rail control.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.5V to 24V - supports 3–4-cell Li+ battery stacks and wide-input adapter operation. |
| 5V SMPS Switching Frequency | 400kHz - enables smaller magnetics and faster transient response for compact notebook designs. |
| 3.3V SMPS Switching Frequency | 500kHz - higher frequency reduces output filter size and improves dynamic performance. |
| Output Voltage Accuracy | ±1.5% - ensures reliable logic supply compliance for CPU, chipset, and memory interfaces. |
| LDO Output Current | 100mA per rail (5V & 3.3V) - sufficient for always-on system functions like RTC, SMBus, and wake logic. |
| Load Transient Response | 100ns - Quick-PWM™ architecture maintains regulation during sudden CPU core state changes. |
| Ultrasonic Mode Threshold | ≥25kHz minimum switching frequency - eliminates audible noise in audio-sensitive subsystems. |
Pinout & Package
MAX1977EEI is housed in a 28-pin QSOP (Quad Small Outline Package) with 0.65mm pitch, thermally enhanced for power management ICs in space-constrained laptop motherboards.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | CS3 | 3.3V SMPS current-sense input - connects to source of synchronous rectifier MOSFET for overcurrent protection. |
| 2 | PGOOD | Open-drain power-good signal - asserts low if either SMPS output deviates >10% from nominal value. |
| 3 | ON3 | 3.3V SMPS enable - high-assertion starts regulator; tied to REF enables sequencing after 5V rail stabilizes. |
| 4 | ON5 | 5V SMPS enable - independent control allows flexible power-up/down sequencing. |
| 5 | ILIM3 | 3.3V current-limit threshold adjust - default 100mV when tied to VCC; adjustable via voltage divider (0.5V–3V). |
| 6 | SHDN | Global shutdown input - pulls device into 6µA standby when below 1.0V trip level. |
| 7 | FB3 | 3.3V feedback input - grounded for fixed 3.3V output; resistive divider enables 2.0V–5.5V adjustable mode. |
| 8 | REF | 2.000V precision reference - powers external circuitry and sets ILIM/feedback thresholds; requires ≥0.22µF bypass. |
| 9 | FB5 | 5V feedback input - grounded for fixed 5V output; same adjustable range as FB3. |
| 10 | PRO | Fault protection enable/disable - GND enables overvoltage/undervoltage lockout; VCC disables for debug or simplified operation. |
| 11 | ILIM5 | 5V current-limit threshold adjust - identical function to ILIM3, supporting independent current limiting per rail. |
| 12 | SKIP | Mode select - GND = pulse-skipping (idle), VCC = fixed-frequency PWM, REF/floating = ultrasonic (>25kHz). |
| 13 | TON | Frequency select - GND selects 400kHz/500kHz (MAX1977 mode); VCC selects 200kHz/300kHz (MAX1777 mode). |
| 14 | BST5 | 5V high-side gate driver boost capacitor node - supplies floating voltage for DH5 driver stage. |
| 15 | LX5 | 5V power inductor switch node - serves as return path for DH5 and current-sense point (MAX1999 only). |
| 16 | DH5 | 5V high-side gate driver output - swings between LX5 and BST5 to drive external N-channel MOSFET. |
| 17 | VCC | Analog supply input - powers internal circuitry; decoupled with 0.1µF ceramic capacitor near pin. |
| 18 | DL5 | 5V low-side gate driver output - drives synchronous rectifier MOSFET with 3.3A sink / 1.7A source capability. |
| 19 | GND | Power and signal ground - common reference for all regulators, drivers, and feedback circuits. |
| 20 | OUT5 | 5V SMPS regulated output - primary logic supply rail; supports up to 5A load with external FETs. |
| 21 | LX3 | 3.3V power inductor switch node - return path for DH3 and current-sense point (MAX1999 only). |
| 22 | DH3 | 3.3V high-side gate driver output - drives external N-channel MOSFET for 3.3V buck stage. |
| 23 | LDO5 | 5V linear regulator output - always-on, bootstrapped from OUT5; delivers 100mA with <3.2Ω switch resistance. |
| 24 | DL3 | 3.3V low-side gate driver output - drives synchronous rectifier with 3.3A sink / 1.7A source capability. |
| 25 | LDO3 | 3.3V linear regulator output - always-on, bootstrapped from OUT3; delivers 100mA with <3.5Ω switch resistance. |
| 26 | OUT3 | 3.3V SMPS regulated output - secondary logic rail; supports up to 5A load with external FETs. |
| 27 | BST3 | 3.3V high-side gate driver boost capacitor node - supplies floating voltage for DH3 driver stage. |
| 28 | N.C. | No connection - not internally bonded; left unconnected on PCB. |
Key Features
| Feature | Design Value |
|---|---|
| Quick-PWM™ control | 100ns load-step response without sense resistors - eliminates board area and power loss from current-sense networks. |
| Ultrasonic pulse-skipping mode | Switching frequency maintained ≥25kHz - prevents audible coil whine in notebook speakers and audio subsystems. |
| Dual-mode feedback (fixed/adjustable) | Single-pin FBx selection between 3.3V/5V fixed or 2.0V–5.5V adjustable output - simplifies BOM and layout reuse. |
| Bootstrapped LDO regulators | 5V/3.3V LDOs auto-enable when respective SMPS rails reach regulation - ensures always-on functionality without external sequencing. |
| Programmable fault protection | PRO pin enables/disables overvoltage (±14%) and undervoltage (70% nominal) shutdown - configurable for safety-critical or debug use cases. |
| Internal soft-start & soft-stop | 1.7ms ramp time and active output discharge - prevents negative voltage spikes and inrush current during startup/shutdown. |
Applications
| Notebook Main Power Supply | Subnotebook System Power |
|---|---|
Use Scenario: Primary DC-DC conversion for CPU, chipset, and memory in 12–15 inch notebooks with 3–4 cell Li+ batteries. IC Role / Device Role / Timing Role: Dual-buck SMPS controller generating 5V and 3.3V logic rails, plus always-on LDOs for real-time clock and firmware execution. Use Value: 400kHz/500kHz operation reduces inductor size by ~30% vs. 200kHz designs, enabling thinner chassis and improved thermal margin. |
Use Scenario: Compact power solution for subnotebooks and ultra-mobile PCs where board area and acoustic noise are critical constraints. IC Role / Device Role / Timing Role: High-frequency dual-output controller with ultrasonic mode to eliminate audible switching noise in proximity to microphones and speakers. Use Value: Pulse-skipping above 25kHz avoids interference with audio band signals, eliminating need for additional EMI shielding or ferrite beads. |
| PDA Power Management | Mobile Communication Device Power |
Use Scenario: Power delivery for handheld PDAs with mixed-voltage peripherals (USB, display, touch controller) and battery life optimization requirements. IC Role / Device Role / Timing Role: Quad-output controller supplying 5V USB host, 3.3V I/O, and two always-on LDOs for wake-on-touch and low-power standby states. Use Value: 6µA shutdown current and programmable SKIP mode extend battery runtime in deep-sleep modes without sacrificing wake latency. |
Use Scenario: Power architecture for 3G/4G mobile hotspots and data cards requiring robust thermal performance and fast transient response during RF transmission bursts. IC Role / Device Role / Timing Role: Dual-buck controller with independent ON3/ON5 enables staggered rail activation to limit inrush during modem initialization. Use Value: 100ns load-step response maintains stable 3.3V/5V rails during sudden 2A RF PA current surges, preventing communication dropouts. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar dual-output SMPS controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1777EEI | 200kHz/300kHz switching frequencies; lower frequency improves light-load efficiency but requires larger magnetics. | Better suited for cost-sensitive, thermally relaxed notebook designs where board area is less constrained. | Select MAX1777EEI when prioritizing peak efficiency at light loads and minimizing EMI over compactness. |
| MAX1999EEI | Pin-selectable 200kHz/300kHz or 400kHz/500kHz operation via TON pin; adds flexibility but increases pin count complexity. | Enables single-BOM support for multiple platform variants (standard/thin-and-light), increasing design reuse. | Choose MAX1999EEI when developing scalable platforms requiring both efficiency and density optimization across product tiers. |
Compared with MAX1777EEI and MAX1999EEI, the MAX1977EEI offers fixed high-frequency operation ideal for space-constrained layouts, while avoiding the configuration overhead of MAX1999EEI's TON-selectable modes - delivering optimal trade-off between size, performance, and design simplicity.
Availability
MAX1977EEI is available at Aetrix Electronics and suitable for notebook computers, subnotebook systems, PDAs, and mobile communication devices requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for MAX1977EEI 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 computing, communications, and industrial applications.
The MAX1777/MAX1977/MAX1999 family was engineered specifically for quad-output main power supplies in portable computing - integrating dual SMPS controllers, bootstrapped LDOs, and advanced sequencing to replace discrete multi-IC solutions in notebook motherboards.
FAQ
What is the operating temperature range for MAX1977EEI?
The MAX1977EEI is rated for operation from –40°C to +85°C, making it suitable for extended-temperature environments found in industrial-grade notebooks and mobile computing equipment. This range is fully specified in the electrical characteristics tables across the full –40°C to +85°C interval, with key parameters including output voltage accuracy, current-limit thresholds, and PGOOD propagation delay guaranteed over this span.
Does MAX1977EEI require external current-sense resistors?
No, the MAX1977EEI does not require external current-sense resistors for basic operation due to its Quick-PWM™ architecture, which senses current through the LX node. However, it retains CS3 and CS5 pins for optional high-accuracy current monitoring or overcurrent protection using external sense resistors - a feature retained for compatibility with MAX1777/MAX1999 pinout and design reuse.
How does the TON pin affect MAX1977EEI functionality?
The TON pin on MAX1977EEI is hardwired to GND per its ordering specification and datasheet configuration table, fixing the device to 400kHz/500kHz operation. Unlike MAX1999EEI, TON has no functional effect on MAX1977EEI - it is reserved for pin compatibility and does not alter switching frequency, control mode, or protection behavior.
Can MAX1977EEI generate adjustable output voltages?
Yes, MAX1977EEI supports adjustable outputs: connecting FB3 or FB5 to a resistive divider between OUT3/OUT5 and GND configures the respective SMPS rail for 2.0V–5.5V regulation. The internal dual-mode comparator recognizes FBx = GND as fixed 3.3V/5V mode and any voltage >0.2V as adjustable mode, with 0.2V threshold ensuring clean mode transition.
What is the purpose of the PRO pin on MAX1977EEI?
The PRO pin on MAX1977EEI enables or disables overvoltage and undervoltage fault protection. When pulled to GND, it activates ±14% overvoltage and 70% undervoltage shutdown with 10ms blanking time; when tied to VCC, protection is disabled - useful during lab validation or when external supervision handles fault response.
MAX1977EEI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 28-SSOP (0.154", 3.90mm Width)
- Packaging:
- Bulk
- Product Status:
- Active
- Applications:
- Controller, Notebook Power System
- Voltage - Input:
- 4.5V ~ 24V
- Number of Outputs:
- 4
- Voltage - Output:
- 2V ~ 3.3V, 5V ~ 5.5V
- Operating Temperature:
- -40°C ~ 85°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-QSOP
MAX1977EEI FAQ
1.How can I place an order for MAX1977EEI through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1977EEI 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 MAX1977EEI reliable?
The price and inventory of MAX1977EEI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1977EEI is usually 5 days.
3.What payment methods are accepted for MAX1977EEI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1977EEI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1977EEI?
MAX1977EEI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1977EEI 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 MAX1977EEI?
For technical support, including MAX1977EEI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1977EEI requirements.
6.How does Aetrix verify that MAX1977EEI is sourced from the original manufacturer or authorized distributors?
All MAX1977EEI 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 MAX1977EEI meets industry standards.
7.What is the process for return or replacement of MAX1977EEI?
All MAX1977EEI units undergo pre-shipment inspection (PSI). If there is an issue with MAX1977EEI, 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 MAX1977EEI part is unused and in its original packaging.
Return procedure for MAX1977EEI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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