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Microchip Technology MIC4685BR
- Part No.:
- MIC4685BR
- Manufacturer:
- Microchip Technology
- Package:
- SPAK-7 (7 Leads + Tab)
- Datasheet:
-
MIC4685BR.pdf
- Description:
- IC REG BUCK ADJ 3A 7SPAK
- Quantity:
- Payment:
- Shipping:
Inventory:4,881
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Product details
Overview
MIC4685BR from Micrel is a 3A adjustable-output synchronous buck regulator in a 7-pin SPAK package, operating at fixed 200kHz PWM with 4V–30V input range and 1.235V feedback reference. It delivers up to 3A continuous output current with >85% efficiency, uses internal NPN switch with bootstrap-enhanced drive (reducing VCE(sat) to 0.59V), and supports point-of-load conversion such as 12V-to-1.8V/3A for embedded power rails.
For engineers reviewing the MIC4685BR datasheet, MIC4685BR pinout, MIC4685BR application, or MIC4685BR equivalent, key selection considerations include its thermal performance in the SPAK package (θJA = 11.8°C/W), enable-controlled shutdown (150µA quiescent), frequency-foldback short-circuit protection, and bootstrap-dependent saturation voltage reduction - all critical for high-current, space-constrained DC/DC designs.
Technical Context
The MIC4685BR implements voltage-mode PWM control using a 1.235V bandgap reference and fixed-frequency 200kHz oscillator, comparing FB voltage against reference via an error amplifier to modulate duty cycle. Its internal NPN power switch is driven by a bootstrap circuit that elevates gate drive above VIN, enabling low-saturation operation even at high duty cycles.
Thermal management relies on the exposed tab (Pin 4) as primary heat path, requiring direct connection to a PCB ground plane acting as heatsink. Protection features include thermal shutdown at 160°C, over-current limiting (3.5–6A), and frequency foldback during hard shorts - all integrated without external components.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4V to 30V (34V transient): Supports wide industrial input rails including 12V and 24V systems with margin for load dump. |
| Output Current | 3A continuous: Delivers full rated current in SPAK package with proper ground-plane thermal design (θJA = 11.8°C/W). |
| Switching Frequency | 200kHz (±25kHz): Fixed PWM enables predictable EMI filtering and simplifies inductor selection (e.g., 39µH standard). |
| Feedback Reference | 1.235V ±2%: Enables precise adjustable output via resistor divider; stable over –40°C to +125°C junction temperature. |
| Saturation Voltage | 0.59V at 1A: Reduced VCE(sat) via bootstrap drive improves efficiency and reduces thermal stress vs. non-boosted alternatives. |
| Quiescent Current | 150µA in shutdown: Minimizes standby power loss when EN pin is pulled low. |
| Protection Features | Thermal shutdown (160°C), frequency-foldback short-circuit, and over-current limit: Fully autonomous fault recovery without external circuitry. |
Pinout & Package
The MIC4685BR is housed in a thermally enhanced 7-pin SPAK (Small Power Air Cooled) package with exposed metal tab (Pin 4) serving as both electrical ground and primary thermal interface. The low-profile (2mm height) footprint occupies 36% less board area than TO-263 while supporting higher power density than TO-220.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BS (Pin 1) | Bootstrap node | Connects external capacitor to generate boosted gate drive voltage; essential for reducing VCE(sat) and maintaining high efficiency at high duty cycles. |
| IN (Pin 2) | Main supply input | Accepts 4V–30V unregulated input; connects directly to collector of internal NPN switch and internal bias regulator. |
| FB (Pin 3) | Feedback input | High-impedance (50nA bias) node tied to error amplifier inverting input; requires resistive divider from VOUT to set output voltage. |
| GND (Pin 4, Tab) | Power and thermal ground | Primary return path for switch current and thermal conduction path; must be soldered to large PCB ground plane for thermal performance. |
| EN (Pin 5) | Enable control | TTL-compatible digital input (2.0V min ON, 0.8V max OFF); pulling low reduces quiescent current to 150µA and disables switching. |
| SW (Pin 6) | Switch emitter output | Drives external inductor and Schottky diode; swings from ~–0.5V (during flyback) to VIN – VCE(sat); high dv/dt node requiring careful layout. |
| NC (Pin 7) | No connect | Internally unconnected; must be tied to GND per datasheet to ensure mechanical stability and EMI control. |
Key Features
| Feature | Design Value |
|---|---|
| SPAK package thermal performance | θJC = 2.2°C/W enables 3A operation with only PCB ground plane as heatsink - eliminates need for external heatsinks in most applications. |
| Bootstrap-enhanced saturation | Reduces VCE(sat) from 1.8V to 0.59V, increasing efficiency from 75% to 88% and lowering thermal dissipation at full load. |
| Integrated protection suite | Combines thermal shutdown, frequency-foldback short-circuit response, and over-current limit - no external sensing or timing components required. |
| Internally compensated loop | Enables stable operation with standard output capacitors (e.g., 330µF tantalum) and fast transient response without external compensation network. |
| Wide input transient tolerance | Withstands 34V transients while operating from 4V–30V nominal input - suitable for automotive and industrial environments with load dump or surge events. |
Applications
| Point-of-Load Conversion | Industrial DC Power Supply |
|---|---|
|
Use Scenario: Converting 12V intermediate bus to 1.8V/3A for FPGA core logic in programmable logic controllers. IC Role / Device Role / Timing Role: Primary buck regulator providing tightly regulated, high-current core voltage with fast transient response to logic switching loads. Use Value: SPAK package enables compact placement near FPGA BGA; bootstrap drive maintains <85% efficiency across 0.1–3A load range without derating. |
Use Scenario: Generating 5V/3A from 24V factory automation rail to power microcontroller, sensors, and I/O drivers. IC Role / Device Role / Timing Role: Main step-down regulator delivering stable 5V with built-in over-current and thermal protection for unattended operation. Use Value: 34V transient rating handles 24V system surges; EN pin allows centralized power sequencing with PLC controller GPIO. |
| Battery Charger Front-End | LCD Panel Power |
|
Use Scenario: Regulating variable solar or battery input (8–30V) to fixed 5V/2A for Li-ion charging IC in portable equipment. IC Role / Device Role / Timing Role: Input-stage buck converter isolating charger IC from wide-input variations and providing clean, ripple-free 5V. Use Value: Wide VIN range accommodates discharged to fully charged battery; frequency-foldback prevents damage during charger short-circuit faults. |
Use Scenario: Supplying 3.3V/2.4A to LCD backlight driver and timing controller in medical display unit. IC Role / Device Role / Timing Role: High-efficiency local regulator converting 12V system rail to low-noise 3.3V for sensitive analog and digital display circuitry. Use Value: Internally compensated loop minimizes output ripple (<50mV pk-pk); thermal shutdown ensures safe operation during extended display-on periods. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar buck regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LM2678-5.0/NOPB | Fixed 5V output, 5A rating, TO-220-5 package, no bootstrap, higher quiescent current (5mA) | Requires redesign for adjustable outputs; lacks transient tolerance (40V max) and thermal performance of SPAK | Select only if fixed 5V output suffices and board space permits larger TO-220 footprint. |
| TPS54331DR | 3A adjustable buck, SOIC-8, 570kHz switching, integrated MOSFETs, no bootstrap, lower max VIN (28V) | Higher frequency enables smaller magnetics but increases EMI sensitivity; no thermal tab limits continuous current without heatsink | Prefer for compact designs where 28V max VIN is acceptable and external heatsinking is impractical. |
Compared with LM2678-5.0/NOPB and TPS54331DR, the MIC4685BR uniquely combines adjustable output, bootstrap-enhanced efficiency, 34V transient tolerance, and SPAK thermal performance - making it optimal for high-reliability 3A point-of-load applications where input variation and thermal constraints coexist.
Availability
MIC4685BR is available at Aetrix Electronics and suitable for point-of-load power supplies, industrial DC power supplies, and battery charger front-ends requiring stable component supply, long-term lifecycle support, and RoHS-compliant manufacturing.
Supply support for MIC4685BR 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
Micrel Inc. was a U.S.-based semiconductor company specializing in power management, analog, and mixed-signal ICs before its acquisition by Microchip Technology in 2015. Known for robust industrial-grade regulators and timing solutions.
The MIC4685BR belongs to Micrel's SuperSwitcher™ family of high-current buck regulators designed specifically for space-constrained, thermally demanding applications requiring >3A output without external MOSFETs or complex compensation.
FAQ
What is the maximum continuous output current of the MIC4685BR under typical conditions?
The MIC4685BR delivers 3A continuous output current when used with proper PCB thermal design - specifically, a large copper ground plane connected to Pin 4 (Tab) to achieve θJA ≤ 11.8°C/W. At ambient temperatures up to 60°C and 12V input, it sustains 3A at 1.8V output with >84% efficiency per typical characteristics data. Derating applies above 83.5°C junction temperature.
Does the MIC4685BR require an external bootstrap diode, and when is it needed?
The MIC4685BR does not require an external bootstrap diode for standard operation - its internal bootstrap circuit uses Pin 1 (BS) and an external capacitor (e.g., 0.33µF/50V) to elevate drive voltage. However, a bootstrap diode (e.g., B120-E3) is recommended only for ultra-low headroom applications like 5V-to-3.3V conversion, and must not be used if VIN exceeds 16V per datasheet guidance.
How does the enable (EN) pin function on the MIC4685BR, and what are its voltage thresholds?
The EN pin on the MIC4685BR is TTL-compatible: a logic-high ≥2.0V enables regulation, while a logic-low ≤0.8V places the device in shutdown mode with 150µA typical quiescent current. It features built-in hysteresis (1.25V window) to prevent noise-induced toggling. If unused, EN must be tied to IN to ensure default operation.
What is the purpose of the NC (Pin 7) on the MIC4685BR, and how should it be handled?
Pin 7 of the MIC4685BR is designated NC (No Connect) and is internally unconnected. Per the official datasheet, it must be tied to GND to ensure mechanical stability, reduce EMI susceptibility, and maintain consistent thermal behavior. Leaving Pin 7 floating may compromise long-term reliability and EMC performance.
Can the MIC4685BR be used in automotive applications, and what are its transient voltage limits?
Yes, the MIC4685BR supports automotive front-end use due to its 34V absolute maximum input rating, which accommodates common 12V system load-dump transients (ISO 7637-2 Pulse 5a). Its –40°C to +125°C junction temperature range and thermal shutdown at 160°C further align with automotive under-hood requirements, though system-level validation remains necessary for AEC-Q100 compliance.
MIC4685BR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Microchip Technology
- Series:
- SuperSwitcher™
- Package/Case:
- SPAK-7 (7 Leads + Tab)
- Packaging:
- Bulk
- Product Status:
- Obsolete
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4V
- Voltage - Input (Max):
- 30V
- Voltage - Output (Min/Fixed):
- 1.235V
- Voltage - Output (Max):
- 28.2V
- Current - Output:
- 3A
- Frequency - Switching:
- 200kHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 7-SPAK
MIC4685BR FAQ
1.How can I place an order for MIC4685BR through Aetrix?
Please submit a Request for Quotation (RFQ) for MIC4685BR 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 MIC4685BR reliable?
The price and inventory of MIC4685BR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MIC4685BR is usually 5 days.
3.What payment methods are accepted for MIC4685BR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MIC4685BR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MIC4685BR?
MIC4685BR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MIC4685BR 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 MIC4685BR?
For technical support, including MIC4685BR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MIC4685BR requirements.
6.How does Aetrix verify that MIC4685BR is sourced from the original manufacturer or authorized distributors?
All MIC4685BR 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 MIC4685BR meets industry standards.
7.What is the process for return or replacement of MIC4685BR?
All MIC4685BR units undergo pre-shipment inspection (PSI). If there is an issue with MIC4685BR, 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 MIC4685BR part is unused and in its original packaging.
Return procedure for MIC4685BR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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