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Analog Devices Inc./Maxim Integrated MAX1843EGI
- Part No.:
- MAX1843EGI
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Package:
- 28-WFQFN Exposed Pad
- Datasheet:
-
MAX1843EGI.pdf
- Description:
- IC REG BUCK ADJ 2.7A 28TQFN
- Quantity:
- Payment:
- Shipping:
Inventory:5,345
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Product details
Overview
MAX1843EGI from Maxim Integrated is a synchronous step-down DC-DC regulator delivering up to 2.7A continuous output current with internal pMOS (90mΩ) and nMOS (70mΩ) switches, 1MHz switching frequency, ±1% output voltage accuracy, and preset +2.5V/+1.8V/+1.5V or adjustable +1.1V–VIN output-designed for CPU I/O ring and chipset supplies in notebook/subnotebook computers.
For engineers reviewing the MAX1843EGI datasheet, MAX1843EGI pinout, MAX1843EGI application, or MAX1843EGI equivalent, key selection considerations include its constant-off-time PWM architecture, Idle Mode™ light-load efficiency optimization, 100% duty-cycle low-dropout operation, thermal shutdown (160°C), and TQFN-28 package with exposed thermal pad.
Technical Context
The MAX1843EGI implements a current-mode, constant-off-time PWM control scheme with programmable off-time (via external RTOFF) enabling switching frequencies up to 1MHz. It operates in continuous-conduction mode above the idle-mode threshold (~0.6A typ) and transitions to pulse-skipping Idle Mode™ below that threshold to maintain high efficiency at light loads.
Its internal synchronous rectification eliminates the need for an external Schottky diode; regulation is achieved by modulating the pMOS on-time while holding off-time constant. The device supports 100% duty-cycle operation when input approaches output voltage, with dropout governed by pMOS RON and inductor DCR.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Output Current | 2.7A continuous - supports high-current CPU I/O and chipset rails without external current sharing. |
| Switching Frequency | Up to 1MHz - enables compact 1–5µH inductors and reduces EMI filtering burden. |
| Input Voltage Range | +3.0V to +5.5V - compatible with standard 3.3V and 5V system rails. |
| Output Voltage Options | +2.5V/+1.8V/+1.5V (pin-selectable) or +1.1V–VIN (adjustable) - covers core logic, memory, and I/O supply requirements. |
| Efficiency | Up to 95% - achieved via synchronous rectification and low RON internal switches (90mΩ pMOS / 70mΩ nMOS @ VIN = +4.5V). |
| Accuracy | ±1% over temperature - ensures stable voltage margins for sensitive digital loads. |
| Shutdown Current | <1µA - meets ultra-low-power system standby requirements. |
Pinout & Package
The MAX1843EGI is housed in a 28-pin Thin Quad Flat No-lead (TQFN) package with an exposed backside thermal pad (pin 13 and pad connected to GND). Thermal performance requires soldering the pad to a large analog ground plane.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| IN (pins 2,4) | Power input for pMOS switch | Accepts +3.0V to +5.5V; must be decoupled near pins with low-ESR ceramic capacitor. |
| LX (pins 3,18,19,23,25) | Switch node | Connects to inductor; carries high di/dt; requires short, wide trace to minimize ringing and losses. |
| PGND (pins 17,20,21) | Power ground return | Internal connection to nMOS source; must tie to input/output capacitor grounds and inductor ground island. |
| GND (pin 13 + backside pad) | Analog ground reference | Separate from PGND in layout; connects to exposed thermal pad for heat dissipation and noise isolation. |
| FBSEL (pin 15) | Output voltage configuration select | Logic level or floating to set +2.5V (VCC), +1.8V (REF), +1.5V (floating), or adjustable (GND). |
| FB (pin 9) | Voltage feedback input | Direct connection to output for fixed voltages; resistive divider for adjustable outputs (VFB = 1.1V nominal). |
| SHDN (pin 27) | Enable/disable control | Logic-low disables all circuitry and disconnects IN from LX; <1µA shutdown current. |
| TOFF (pin 8) | Off-time programming | Resistor-to-GND sets tOFF (0.4–4µs), directly determining switching frequency and transient response. |
Key Features
| Feature | Design Value |
|---|---|
| Idle Mode™ operation | Skips switching cycles under light load to reduce gate charge and transition losses-maintains >85% efficiency at 10mA output. |
| Adjustable soft-start | Capacitor on SS pin (pin 6) controls inrush current ramp rate-prevents input rail collapse during power-up or wake-from-standby. |
| 100% duty-cycle mode | Enables dropout operation down to VIN – VOUT ≈ IOUT × RON,P-critical for battery-powered systems nearing end-of-life voltage. |
| Integrated compensation | COMP pin (pin 7) accepts single 470pF capacitor to VCC-simplifies loop stability tuning without external op-amp network. |
| Output short-circuit protection | Current limit trips at 3.1–4.1A (typical 3.6A); forces extended off-time (≈4×tOFF) if VOUT drops below 25% of nominal-prevents thermal runaway. |
Applications
| CPU I/O Ring Supply | Chipset Core Voltage |
|---|---|
Use Scenario: Powering the interface voltage domain between CPU die and northbridge/southbridge in portable x86 platforms. IC Role / Device Role / Timing Role: Primary synchronous buck regulator delivering tightly regulated +1.8V or +2.5V at up to 2.7A with fast line/load transient response. Use Value: Maintains ±1% output accuracy across -40°C to +85°C while achieving 95% peak efficiency-reducing thermal load on compact motherboard layouts. | Use Scenario: Generating core voltage for Intel/AMD chipset components requiring stable +1.5V with dynamic current demand. IC Role / Device Role / Timing Role: Adjustable-output buck converter configured for +1.5V via FBSEL floating, supporting precise margining and aging compensation. Use Value: Programmable constant-off-time architecture allows frequency optimization (e.g., 1.07MHz at +2.5V out) to balance EMI, inductor size, and light-load efficiency. |
| Notebook System Rail | Subnotebook Low-Power Domain |
Use Scenario: Converting 5V main battery rail to +3.3V or +2.5V for peripheral controllers, USB hubs, and display interfaces. IC Role / Device Role / Timing Role: High-efficiency step-down regulator operating from +3.0V to +5.5V input, featuring thermal shutdown and undervoltage lockout (2.6V). Use Value: Internal synchronous switches eliminate external diode, reducing BOM count and PCB area-critical for space-constrained clamshell designs. | Use Scenario: Powering ARM-based subnotebook SoCs with variable load profiles including deep-sleep states. IC Role / Device Role / Timing Role: Constant-off-time controller with Idle Mode™-dynamically shifts between PWM and pulse-skipping to sustain >80% efficiency from 10mA to 2.7A. Use Value: <1µA shutdown current and adjustable soft-start enable compliance with ACPI S3/S5 power states and reduce battery drain during long idle periods. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar synchronous step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TPS54227PWP | Fixed 500kHz frequency; lower max output current (2.2A); no Idle Mode™; requires external bootstrap capacitor. | Less suited for ultra-light-load efficiency-critical applications; lacks programmable off-time and 100% duty-cycle mode. | Choose for cost-sensitive designs where 500kHz EMI profile and simpler layout outweigh efficiency trade-offs. |
| RT8205AZSP | Supports wider input (4.5–24V); higher RON (120mΩ/100mΩ); no integrated soft-start capacitor control; different pinout. | Better for industrial 12V-input systems; not pin-compatible; requires redesign of feedback and timing networks. | Prefer when input exceeds 5.5V or when board-level thermal management favors larger package footprint. |
Compared with TPS54227PWP and RT8205AZSP, the MAX1843EGI provides superior light-load efficiency via Idle Mode™, finer frequency control through RTOFF, and seamless low-dropout operation-making it optimal for battery-powered portable computing rails where efficiency across full load range is critical.
Availability
MAX1843EGI is available at Aetrix Electronics and suitable for notebook power delivery, chipset voltage regulation, and CPU I/O ring applications requiring stable component supply, long-term lifecycle support, and guaranteed lead-free compliance.
Supply support for MAX1843EGI 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 markets.
The MAX1843EGI belongs to Maxim's high-efficiency synchronous buck regulator product line, engineered specifically for low-voltage, high-current power conversion in space- and thermally-constrained portable computing platforms.
FAQ
What is the maximum continuous output current supported by the MAX1843EGI?
The MAX1843EGI delivers up to 2.7A continuous output current under typical thermal conditions (with proper PCB copper area and airflow). Its internal pMOS and nMOS switches have on-resistances of 90mΩ and 70mΩ respectively at VIN = +4.5V, enabling this current level while maintaining high efficiency and thermal safety within its 150°C junction limit.
How does the MAX1843EGI achieve high efficiency at light loads?
The MAX1843EGI uses Maxim's proprietary Idle Mode™, which skips switching cycles when load current falls below ~0.6A. This reduces gate-charge and transition losses significantly-maintaining >85% efficiency even at 10mA output. Unlike forced-PWM regulators, the MAX1843EGI dynamically transitions between constant-off-time PWM and Idle Mode™ without external control.
Can the MAX1843EGI operate in 100% duty-cycle mode, and what is its practical dropout voltage?
Yes, the MAX1843EGI enters 100% duty-cycle mode when input voltage approaches output voltage. Dropout voltage equals IOUT × RON,P + IOUT × DCRINDUCTOR; at 1A and VIN = +3.0V, measured dropout is 250mV. This mode sustains regulation without external components, making the MAX1843EGI suitable for battery-powered systems nearing end-of-discharge.
What is the role of the TOFF pin on the MAX1843EGI, and how is it used in design?
The TOFF pin (pin 8) sets the constant off-time via an external resistor to GND, directly determining switching frequency and transient response. Using RTOFF = 110kΩ yields ~1.0µs off-time and ~1MHz operation at VIN = +5V/VOUT = +2.5V. Designers select RTOFF using the formula RTOFF = (tOFF − 0.07µs) × (110kΩ/1.00µs) to optimize efficiency, noise, and component size for their specific application.
Does the MAX1843EGI require an external Schottky diode, and why or why not?
No, the MAX1843EGI does not require an external Schottky diode because it integrates both a 90mΩ pMOS high-side switch and a 70mΩ nMOS synchronous rectifier. These internal switches replace the diode path during inductor discharge, eliminating forward-voltage conduction losses and improving efficiency-especially at high currents and low output voltages-while reducing bill-of-materials and PCB area.
MAX1843EGI Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc./Maxim Integrated
- Series:
- -
- Package/Case:
- 28-WFQFN Exposed Pad
- Packaging:
- Bulk
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable (Programmable)
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 3V
- Voltage - Input (Max):
- 5.5V
- Voltage - Output (Min/Fixed):
- 1.1V (1.5V, 1.8V, 2.5V)
- Voltage - Output (Max):
- 5.5V
- Current - Output:
- 2.7A
- Frequency - Switching:
- 1MHz
- Synchronous Rectifier:
- Yes
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 28-TQFN (5x5)
MAX1843EGI FAQ
1.How can I place an order for MAX1843EGI through Aetrix?
Please submit a Request for Quotation (RFQ) for MAX1843EGI 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 MAX1843EGI reliable?
The price and inventory of MAX1843EGI are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MAX1843EGI is usually 5 days.
3.What payment methods are accepted for MAX1843EGI?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MAX1843EGI transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MAX1843EGI?
MAX1843EGI orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MAX1843EGI 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 MAX1843EGI?
For technical support, including MAX1843EGI datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MAX1843EGI requirements.
6.How does Aetrix verify that MAX1843EGI is sourced from the original manufacturer or authorized distributors?
All MAX1843EGI 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 MAX1843EGI meets industry standards.
7.What is the process for return or replacement of MAX1843EGI?
All MAX1843EGI units undergo pre-shipment inspection (PSI). If there is an issue with MAX1843EGI, 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 MAX1843EGI part is unused and in its original packaging.
Return procedure for MAX1843EGI:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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