MBI6651 — 36V 1.2A Step-Down Constant-Current LED Driver

Overview

The MBI6651 (MBI6651GSD) is a step-down (buck) constant-current LED driver IC manufactured by Macroblock Inc. Packaged in a SOT-23-6, TO-252-5, or SOP-8 enclosure, it drives high-power LEDs at continuous currents up to 1.2 Amperes from supply voltages ranging from 9.0V to 36.0V DC.

Operating at switching frequencies up to 1.0 MHz, the MBI6651 uses high-side current sensing with a low 100 mV reference voltage ( $V_{SEN}$ ) to maximize efficiency (up to $96\%$ ). Its multi-function DIM pin accepts both high-frequency PWM dimming signals ( $100\text{ Hz} \dots 1\text{ kHz}$ ) and DC voltage analog dimming ( $0.5\text{V} \dots 2.5\text{V}$ ).

Quick reference


Input Supply Voltage (`VIN`)	9.0 V to 36.0 V DC
Output LED Current	Up to $1.2\text{ A}$ continuous (Set by sense resistor $R_{SEN}$ )
Sense Voltage (`VSEN`)	$100\text{ mV}$ low-loss high-side threshold
Switching Frequency	Up to $1.0\text{ MHz}$
Efficiency	Up to $96\%$ typical
Dimming Modes	PWM Dimming ( $100\text{ Hz} \dots 1\text{ kHz}$ ) & DC Analog Voltage Dimming
Package	SOT-23-6 / TO-252-5 / SOP-8

Pinout (SOT-23-6 Package)

text

             ┌───┴───┐
        SW  1│ 1   6 │ VIN (+9V to +36V)
       GND  2│       │ 5 SEN (Sense Input)
       DIM  3│MBI6651│ 4 NC
             └───────┘

Pin	Name	Type	Description
1	`SW`	Output	Internal MOSFET Switch Drain (Connect to Schottky Diode & Inductor)
2	`GND`	Power	Ground Reference (0 V)
3	`DIM`	Input	Dimming Control Input (Open = 100% LED Current; Low = Shutdown; PWM or Analog Input)
4	`NC`	Unused	No Internal Connection
5	`SEN`	Input	High-Side Current Sense Input ( $100\text{ mV}$ reference relative to VIN)
6	`VIN`	Power	Power Supply Input (+9.0V to +36.0V DC)

LED Current Programming Formula

$I_{LED} = \frac{100\text{ mV}}{R_{SEN}} = \frac{0.10\text{V}}{R_{SEN}}$

$\text{For } I_{LED} = 1.0\text{ A} \implies R_{SEN} = \frac{0.10\text{V}}{1.0\text{A}} = 0.10\ \Omega\ \ (1\text{W}).$

Common mistakes

Leaving DIM (Pin 3) grounded: DIM pulled below $0.4\text{V}$ places the chip in shutdown mode ( $0\text{ mA}$ ). For 100% continuous output brightness, leave DIM floating or pull HIGH to $V_{IN}$ / 3.3V / 5V.

Notes

MBI6651 vs PT4115: MBI6651 supports up to 36V input voltage range; PT4115 supports up to 30V input voltage range. Both use 100mV high-side current sense.