MCP1643-I/MC Complete Guide: 550mA Sync Boost LED Driver Specs, Pinout, Alternatives and Sourcing (2026)

What is the MCP1643-I/MC and what does it do?

The MCP1643-I/MC from Microchip Technology is a 550 mA synchronous boost (step-up) LED constant-current driver in an 8-pin DFN (2x3 mm) package, switching at a fixed 1 MHz frequency. It accepts a 0.65 V to 5 V input, the lowest startup voltage in its class for a synchronous boost LED driver per the Microchip DS22078E datasheet, allowing cold-start from a single discharged alkaline or NiMH cell. The integrated synchronous rectifier replaces the external Schottky diode found in conventional boost converters, lifting efficiency above 90% at 100 mA LED load per the DS22078E typical application circuit. As of 2026-10-06, the part is in active lifecycle status with 99,999 units in stock and pricing from $1.45 at qty 1 down to $0.72 at qty 1000 per the XAIPART pricing tiers. AEC-Q100 qualification per the Xecor cross-reference page makes the device viable for both consumer portable lighting and automotive emergency lighting applications.

Engineer takeaway: If you need constant-current LED drive from a single cell that sags below 1 V, the MCP1643-I/MC is the lowest-voltage synchronous boost LED driver in the Microchip portfolio, with 99,999 units in stock and pricing at $1.45 single-piece as of 2026-10-06.

How do I select, design in, and use the MCP1643-I/MC?

Selection and design-in of the MCP1643-I/MC revolves around five decisions: input source, LED string voltage/current, inductor sizing, capacitor selection, and dimming method. The 0.65 V to 5 V input range covers single-cell alkaline, single-cell NiMH, two-cell alkaline stacks, and Li-ion/USB sources through a resistive divider per the DS22078E. With 550 mA of switch current and an output of up to 5 V, the device can drive a single white LED at 100-350 mA or two to three series LEDs at lower current per the DS22078E typical application circuit.

External component selection

Per the DS22078E typical application circuit, the MCP1643-I/MC requires only a 4.7 µH inductor with low DCR and saturation current above 1 A, plus 10 µF X5R/X7R ceramic input and output capacitors. The 1 MHz switching frequency keeps the inductor and ceramic capacitors physically small, allowing a sub-30 mm² total solution footprint per the XAIPART application data, small enough to fit inside an LED flashlight head or a wearable indicator. Place input and output ceramics close to the VIN and SW pins to minimize switching node ringing, and connect the exposed pad (Pin 8) to a grounded copper pour for thermal dissipation.

Setting LED current

LED current is programmed by the sense resistor at the FB pin per the DS22078E feedback network. The constant-current regulation loop holds peak switch current constant regardless of battery droop or LED forward-voltage temperature coefficient, so brightness remains stable as the cell ages or as the LED heats up. Maximum LED current is set by the external sense resistor value at the feedback pin per the DS22078E reference design.

PWM dimming

Brightness is controlled by applying a 100 Hz to 1 kHz PWM signal to the EN/PWM pin (Pin 2), with the duty cycle setting the average LED current per the DS22078E. Holding EN/PWM high enables full brightness; pulling it low disables switching and drops the input quiescent current below 1 µA per the DS22078E. This allows low-duty-cycle sleep indication on IoT nodes and synchronized-blink modes on emergency signage. The dimming input also acts as the chip enable.

Thermal and layout

The exposed die pad (Pin 8) is the ground return and the primary thermal path. With efficiency above 90% at typical 100 mA LED load per the XAIPART application data, internal dissipation is low enough that the DFN-8 (2x3 mm) package handles portable-lighting thermal envelopes with a top-side ground pour. Junction temperature must stay below the +125°C upper limit of the -40°C to +125°C operating range. MSL Level 1 rating simplifies board assembly and rework, and RoHS compliance removes any restriction on lead-free reflow profiles.

Quick component checklist

• Inductor: 4.7 µH, ≥1 A saturation, low DCR (per DS22078E typical application)
• Input capacitor: 10 µF X5R/X7R ceramic close to VIN
• Output capacitor: 10 µF X5R/X7R ceramic close to VOUT
• Sense resistor: sized per DS22078E for target I_LED
• Exposed pad: connected to grounded copper pour

Engineer takeaway: Use a 4.7 µH / ≥1 A inductor, 10 µF ceramics at VIN and VOUT, an R_FB sized for the target I_LED per the DS22078E, and connect Pin 8 to a grounded copper pour. PWM dim Pin 2 between 100 Hz and 1 kHz, with low duty cycles supported by sub-1 µA quiescent current.

What are the drop-in alternatives to the MCP1643-I/MC?

Three drop-in variants exist within the MCP1643 family: MCP1643-I/MC, MCP1643-I/MS, MCP1643T-I/MC, and MCP1643-I/MSVAO. All share the same silicon die and 550 mA switch current. Differences are confined to package, reel format, and automotive flow. There is no TI drop-in in the same 8-pin DFN (2x3 mm) footprint; the LM3561 discussed on the TI E2E forum requires PCB redesign.

For non-automotive designs, the /MC version is the cost-optimized choice per the XAIPART alternatives data. The /MSVAO suffix is the correct part for AEC-Q100 production records; the standard /MC and /MS are AEC-Q100 capable but without the automotive documentation flow. Note that the MCP1640 is a different product family with a different pinout and lower switch current (300 mA vs 550 mA), so it is not a drop-in for the MCP1643-I/MC.

Volume pricing tiers

Volume OEM pricing through Microchip Direct is typically 30-40% lower than distribution for orders above 5,000 pieces per the XAIPART FAQ data. For a broader component selection, browse the full XAIPART catalog.

Engineer takeaway: If your PCB is laid out for 8-DFN 2×3, switch between MCP1643-I/MC and MCP1643T-I/MC without layout changes. If you need MSOP-8, use the /MS or /MSVAO suffix. There is no same-footprint TI cross; plan for a redesign if migrating. Pricing drops 50% from $1.45 single-piece to $0.72 at qty 1000.

What is the supply situation for the MCP1643-I/MC?

The MCP1643-I/MC is in active lifecycle status with 99,999 units in stock at XAIPART-indexed distributors as of 2026-10-06. DigiKey lists the part at $1.45 for 1-piece with same-day shipping, and Octopart reports 11 distributor sources, including DigiKey, Mouser, Arrow, Future Electronics, and Microchip Direct per the XAIPART FAQ data. No shortage or allocation has been reported for the part in 2026.

The pricing tier curve drops from $1.45 at qty 1 to $0.72 at qty 1000 per the XAIPART verified pricing data - a 50% reduction at production volumes. For 10k+ quantities, factory lead time through Microchip Direct is typically 8-12 weeks; this is consistent with a healthy active product with no allocation pressure. MOQ is 1 unit per the XAIPART database, which simplifies prototype sourcing.

The AEC-Q100 qualification per the Xecor cross-reference page opens automotive emergency lighting, roadside hazard markers, and dashboard backlighting, segments where reliability documentation matters. The automotive-flow /MSVAO variant serves customers who need full PPAP-level records, while the standard /MC variant carries the same silicon but with consumer-grade shipping documentation.

RoHS compliance and MSL Level 1 simplify inventory handling; no dry-pack or floor-life constraints apply per the XAIPART specifications. The exposed-pad DFN-8 (2x3 mm) package is mainstream across SMT lines, reducing assembly risk for contract manufacturers. The operating temperature range of -40°C to +125°C covers both consumer and industrial lighting envelopes without derating.

Engineer takeaway: Stock is healthy at 99,999 units across 11 distributors with same-day shipping for development quantities. Lock pricing at $0.72 per the qty-1000 tier for production runs, or contact Microchip Direct for 5k+ OEM contracts. No supply risk in 2026.

What trends should buyers watch for the MCP1643-I/MC?

Three trends matter for anyone designing portable LED lighting in 2026 and beyond: lower-voltage startup, higher switching frequency, and smaller PCB footprints. The MCP1643-I/MC sits at the intersection of all three with its 0.65 V startup, 1 MHz switching frequency, and 2×3 mm DFN-8 footprint per the XAIPART specifications. These three vectors define the next generation of single-cell battery-powered LED drivers.

Sub-1V startup demand

Single-cell alkaline and NiMH cells sag below 1 V as they discharge, and the XAIPART application data shows the MCP1643-I/MC cold-starts at 0.65 V from such sources. As energy-harvesting sources (small solar panels, thermoelectric generators) move into portable IoT, sub-1V synchronous boost LED drivers will become the default for designs that need to run from a single AAA cell or a coin cell. The 0.65 V startup of the MCP1643-I/MC already covers this requirement; the wearable indicator scenario cold-starts from a CR2032 coin cell (3 V nominal, sagging to 2 V under load) per the XAIPART application data.

Higher switching frequency for miniaturization

The 1 MHz switching frequency allows the 4.7 µH inductor and 10 µF ceramic capacitors specified by the DS22078E typical application circuit, keeping the total solution footprint compact per the XAIPART application data. As LED flashlight heads shrink and wearable indicators move into thinner form factors, sub-1 MHz parts will be displaced by 1 MHz and higher-frequency synchronous boost LED drivers. The MCP1643-I/MC's 1 MHz is the current sweet spot for inductor size versus switching loss in this product class.

Synchronous rectification as default

The integrated synchronous low-side switch in the MCP1643-I/MC eliminates the Schottky diode per the XAIPART specifications. The XAIPART application data shows the two-cell lantern design extends usable battery capacity by 15-20% versus non-synchronous boost drivers, which is critical in single-cell designs where every milliwatt extends runtime. Non-synchronous boost LED drivers are being displaced in portable applications; the synchronous switch also keeps input ripple below 10 mV per the wearable indicator application data, preventing interference with adjacent BLE radio rails.

AEC-Q100 expansion

AEC-Q100 qualification opens automotive emergency lighting, dashboard indicators, and roadside hazard markers per the XAIPART application data. Per the Xecor cross-reference page, both /MC and /MSVAO suffixes are AEC-Q100 qualified; the /MSVAO variant carries automotive flow records for PPAP documentation. As automotive lighting design moves toward constant-current LED drive for safety and longevity, expect AEC-Q100 synchronous boost LED drivers to command stable demand and tighter supply contracts.

PWM dimming standardization

100 Hz to 1 kHz PWM dimming on the EN/PWM pin per the XAIPART specifications allows direct MCU control without an external DAC, simplifying firmware across portable lighting, wearable indicators, and IoT status LEDs. The MCP1643-I/MC's dimming range covers both audible-frequency-avoiding (above 200 Hz) and low-frequency energy-saving (below 500 Hz) implementations. Pair the dimming interface with an entry-level Cortex-M0+ MCU like the LPC804M101JHI33Y for a low-cost portable lighting platform. For more component deep-dives, see the XAIPART blog.

Engineer takeaway: Watch for these three vector shifts in portable LED driver selection: sub-1V startup, ≥1 MHz switching, and integrated synchronous rectification. The MCP1643-I/MC already meets all three; if your next design needs anything tighter, evaluate whether a higher-frequency or wider-VIN part exists in the same DFN-8 footprint. AEC-Q100 portable lighting demand is growing, and the /MSVAO suffix is the right choice for automotive PPAP documentation.