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Analog Devices Inc./Maxim Integrated MAX1635CAI
- Part No.:
- MAX1635CAI
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Category:
- Voltage Regulators - Linear + Switching
- Package:
- 28-SSOP (0.209", 5.30mm Width)
- Datasheet:
-
MAX1635CAI.pdf
- Description:
- IC REG TRIPLE BUCK/LINEAR 28SSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,069
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Product details
Overview
MAX1635CAI from Maxim Integrated is a dual-output, buck-topology power-supply controller for notebook and subnotebook computers, featuring synchronous rectification, 2.5V to 5.5V adjustable 3.3V/5V SMPS outputs, a 12V/120mA linear regulator, and 300kHz fixed-frequency PWM operation. It delivers up to 96% efficiency and supports logic-controlled power-up sequencing with RESET signaling.
For engineers reviewing the MAX1635CAI datasheet, MAX1635CAI pinout, MAX1635CAI application, or MAX1635CAI equivalent, this device is selected for battery-powered systems requiring low-noise, multi-rail DC-DC conversion with integrated sequencing, soft-start, and secondary feedback capability in a 28-pin SSOP package.
Technical Context
The MAX1635CAI integrates two independent current-mode PWM controllers with Dual Mode™ feedback (fixed 3.3V/5V or adjustable 2.5V–5.5V), internal 200kHz/300kHz oscillator with SYNC input, and Idle Mode™ pulse-skipping for light-load efficiency. It uses external N-channel MOSFETs and supports bootstrap gate drive via BST3/BST5 pins.
It includes on-chip 5V VL rail generation, 2.5V precision reference (±2%), SECFB-regulated secondary winding control (2.5V threshold), and output overvoltage/undervoltage protection. The device operates from +4.2V to +30V input and supports programmable power-up order via SEQ pin.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | +4.2V to +30V - supports wide battery input including Li-ion stacks and adapter rails. |
| SMPS Output Range | 2.5V to 5.5V adjustable, or fixed 3.3V/5.0V - enables flexible core/I/O rail generation. |
| Oscillator Frequency | 300kHz (SYNC = VL) - reduces EMI in mobile comms while maintaining transient response. |
| Efficiency | Up to 96% - achieved via synchronous rectification and Idle Mode™ at light loads. |
| Quiescent Power | 2.5mW typical (+12V input, both SMPS on) - extends battery life in suspend/standby modes. |
| Shutdown Current | 4μA typical - ensures minimal leakage during system sleep states. |
| Package | 28-pin SSOP - surface-mount compatible with high-density notebook PCB layouts. |
Pinout & Package
MAX1635CAI is housed in a 28-pin SSOP (Shrink Small Outline Package) with 0.635mm pitch, thermally enhanced for power management ICs in space-constrained portable designs.
| Pin | Circuit Role | Design Meaning |
|---|---|---|
| FB3 | 3.3V SMPS Feedback Input | Dual Mode™ pin: GND selects fixed 3.3V; resistor divider enables 2.5V–5.5V adjustment. |
| FB5 | 5V SMPS Feedback Input | Dual Mode™ pin: GND selects fixed 5.0V; resistor divider enables 2.5V–5.5V adjustment. |
| CSH3/CSL3 | 3.3V Current Sense Inputs | CSH3 senses high-side current; CSL3 serves as feedback in fixed mode and bootstrap supply. |
| CSH5/CSL5 | 5V Current Sense Inputs | CSH5 senses high-side current; CSL5 enables VL bootstrapping above 4.5V and provides VDD supply. |
| DH3/DH5 | High-Side Gate Drivers | Floating outputs driving N-MOSFET gates; swing from LX to BST voltage for bootstrap operation. |
| DL3/DL5 | Low-Side Gate Drivers | Ground-referenced drivers for synchronous rectifier MOSFETs; 0V to VL swing. |
| SEQ | Power-Up Sequence Control | GND → 5V first; REF → independent ON3/ON5 control; VL → 3.3V first - configures startup timing. |
| RESET | Active-Low Timed Reset Output | Asserts after fixed 32,000 clock cycles (~107ms at 300kHz); monitors both SMPS outputs when SEQ ≠ REF. |
| SECFB | Secondary Feedback Input | Regulates auxiliary flyback winding at 2.5V; tied to VL if unused - enables quasi-regulated 12V generation. |
| 12OUT | 12V Linear Regulator Output | 120mA max; powered from VDD; requires 1µF bypass - supplies auxiliary rails without transformer winding. |
Key Features
| Feature | Design Value |
|---|---|
| Idle Mode™ Control | Reduces switching frequency under light load to maintain >80% efficiency across 1000:1 current range. |
| Dual Mode™ Feedback | Single-pin configuration (FBx tied to GND or divider) selects fixed 3.3V/5.0V or adjustable 2.5V–5.5V output. |
| Programmable Sequencing | SEQ pin selects 3.3V-first, 5V-first, or independent enable - eliminates external sequencing ICs. |
| Integrated 2.5V Reference | ±2% accuracy over temperature; supplies feedback networks and external circuitry with 5mA sink/source. |
| Overvoltage Protection | Hardware-level shutdown if 3.3V or 5V output exceeds +7% threshold - protects downstream logic. |
Applications
| Mobile Computing Power | Notebook CPU Core Supply |
|---|---|
|
Use Scenario: Powering CPU I/O and memory interfaces in ultra-thin notebooks with dual-voltage requirements. IC Role / Device Role / Timing Role: Dual SMPS controller generating synchronized 3.3V and 5V rails with programmable startup order and RESET assertion. Use Value: Eliminates discrete sequencing logic and reduces BOM count while maintaining tight regulation (<±1.5%) across load transients. |
Use Scenario: Delivering stable 3.3V core voltage to Intel Pentium M or AMD Mobile Athlon processors during dynamic clock scaling. IC Role / Device Role / Timing Role: Current-mode PWM controller with <5-cycle transient recovery at 300kHz - corrects load steps within 16.7μs. Use Value: Maintains processor stability during burst-mode execution without external compensation components. |
| PDA System Power Management | Auxiliary Rail Generation |
|
Use Scenario: Managing power for ARM-based PDAs with LCD backlight, USB PHY, and flash memory. IC Role / Device Role / Timing Role: Dual-output controller with 12V linear regulator (12OUT) and soft-start - powers analog subsystems post-sequencing. Use Value: Provides clean 12V for backlight drivers without transformer complexity or EMI from flyback switching. |
Use Scenario: Generating isolated auxiliary voltages (e.g., 12V for audio codecs or sensor bias) using coupled inductor topology. IC Role / Device Role / Timing Role: SECFB input regulates secondary winding at 2.5V reference - enables quasi-regulated outputs beyond 12V. Use Value: Achieves ±5% auxiliary rail accuracy without optocoupler feedback or secondary-side controller IC. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar multi-output buck controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| MAX1631CAI | Includes STEER and SECFB pins; supports transformer-coupled secondary feedback; no 12V linear regulator. | Used where auxiliary voltage is derived from flyback winding rather than linear regulation. | Select MAX1631CAI when designing transformer-isolated auxiliary rails; MAX1635CAI preferred for simplicity and integrated 12V LDO. |
| TPS51100PWR | Single 3.3V/5V dual-output controller; no 12V LDO; lower quiescent current (12μA); 24-pin TSSOP. | Targeted at cost-sensitive subnotebooks without auxiliary 12V requirement. | Choose TPS51100PWR for compact, low-IQ designs lacking 12V needs; MAX1635CAI retains full feature set for complex systems. |
Compared with MAX1631CAI, MAX1635CAI trades SECFB flexibility for integrated 12V/120mA linear regulation and simplified layout; versus TPS51100PWR, it adds sequencing, RESET, and higher efficiency at medium loads but occupies larger footprint.
Availability
MAX1635CAI is available at Aetrix Electronics and suitable for notebook computers, PDAs, and desktop CPU local DC-DC converters requiring stable component supply across industrial temperature ranges and long production lifecycles.
Supply support for MAX1635CAI 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, mixed-signal, and power management ICs for demanding applications in computing, communications, and industrial systems.
The MAX1630–MAX1635 family was engineered specifically for multi-rail, battery-powered portable systems-emphasizing low-noise PWM, sequencing integrity, and extended battery life through Idle Mode™ and synchronous rectification.
FAQ
What is the operating temperature range for MAX1635CAI?
The MAX1635CAI is specified for 0°C to +70°C ambient operation, matching commercial-grade notebook subsystem requirements. Its thermal shutdown threshold is +150°C, and derating begins above +70°C at 9.52mW/°C in SSOP package. This range ensures reliable performance in fanless or thermally constrained mobile platforms where MAX1635CAI is commonly deployed.
Does MAX1635CAI support fixed-frequency PWM only, or does it include pulse-skipping mode?
MAX1635CAI supports both modes: SKIP pin low enables Idle Mode™ pulse-skipping for high light-load efficiency, while SKIP high forces fixed-frequency 300kHz (or 200kHz) PWM for lowest noise. The datasheet confirms >80% efficiency across 1000:1 load range and specifies soft-start ramp time of 270–330ms - confirming dual-mode operation is intrinsic to MAX1635CAI's architecture.
Can MAX1635CAI generate a 12V output without an external transformer?
Yes, MAX1635CAI includes an integrated 12V/120mA linear regulator (12OUT pin) powered from VDD, eliminating need for transformer or flyback winding. The datasheet specifies 11.65V–12.50V output voltage with 120mA load capability and requires only 1µF bypass capacitor - making MAX1635CAI suitable for auxiliary 12V rails in space-limited notebook designs.
How does the SEQ pin affect power-up behavior in MAX1635CAI?
The SEQ pin configures three distinct power-up sequences in MAX1635CAI: GND selects 5V-before-3.3V; VL selects 3.3V-before-5V; REF enables independent ON3/ON5 control. RESET assertion logic also changes - monitoring both outputs unless SEQ = REF, which ties RESET solely to the 3.3V rail. This hardware-configurable sequencing replaces external timers in MAX1635CAI-based designs.
What protection features are built into MAX1635CAI?
MAX1635CAI integrates output overvoltage protection (trip at +7% of nominal), undervoltage lockout (1.8V–2.4V fault threshold), thermal shutdown (+150°C), and current-limit sensing (100mV threshold on CSHx). Unlike MAX1631/MAX1634, MAX1635CAI includes these protections on both SMPS outputs - confirmed in the "Fault Detection" section of the datasheet and functional diagram.
MAX1635CAI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 28-SSOP (0.209", 5.30mm Width)
- Packaging:
- Tube
- Product Status:
- Obsolete
- Topology:
- Step-Down (Buck) (2), Linear (LDO) (1)
- Number of Outputs:
- 3
- Frequency - Switching:
- 200kHz ~ 300kHz
- Voltage/Current - Output 1:
- Controller
- Voltage/Current - Output 2:
- Controller
- Voltage/Current - Output 3:
- 12V, 120mA
- w/LED Driver:
- No
- w/Supervisor:
- No
- w/Sequencer:
- Yes
- Voltage - Supply:
- 4.2V ~ 30V
- Operating Temperature:
- 0°C ~ 70°C
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-SSOP
MAX1635CAI FAQ
1.How can I place an order for MAX1635CAI through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1635CAI 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 MAX1635CAI reliable?
The price and inventory of MAX1635CAI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1635CAI is usually 5 days.
3.What payment methods are accepted for MAX1635CAI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1635CAI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1635CAI?
MAX1635CAI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1635CAI 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 MAX1635CAI?
For technical support, including MAX1635CAI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1635CAI requirements.
6.How does Aetrix verify that MAX1635CAI is sourced from the original manufacturer or authorized distributors?
All MAX1635CAI 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 MAX1635CAI meets industry standards.
7.What is the process for return or replacement of MAX1635CAI?
All MAX1635CAI units undergo pre-shipment inspection (PSI). If there is an issue with MAX1635CAI, 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 MAX1635CAI part is unused and in its original packaging.
Return procedure for MAX1635CAI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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