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ML4425

Fairchild
Part Number ML4425
Manufacturer Fairchild
Description Sensorless BLDC Motor Controller
Published May 7, 2005
Detailed Description www.fairchildsemi.com ML4425 Sensorless BLDC Motor Controller Features • • • • • • Stand-alone operation Motor starts a...
Datasheet PDF File ML4425 PDF File

ML4425
ML4425

Overview
www.
fairchildsemi.
com ML4425 Sensorless BLDC Motor Controller Features • • • • • • Stand-alone operation Motor starts and stops with power to IC On-board start sequence: Align ♦ Ramp ♦ Set Speed Patented Back-EMF commutation technique provides jitterless torque for minimum “spin-up” time Onboard speed control loop PLL used for commutation provides noise immunity from PWM spikes, compared to noise sensitive zero crossing technique PWM control for maximum efficiency Direct FET drive for 12V motors; drives high voltage motors with IC buffers General Description The ML4425 PWM motor controller provides all of the functions necessary for starting and controlling the speed of delta or wye wound Brushless DC (BLDC) motors without Hall Effect sensors.
Back EMF voltage is sensed from the motor windings to determine the proper commutation phase sequence using a PLL.
This patented sensing technique will commutate a wide range of 3-Phase BLDC motors and is insensitive to PWM noise and motor snubbing circuitry.
The ML4425 limits the motor current using a constant offtime PWM control loop.
The velocity loop is controlled with an onboard amplifier.
The ML4425 has circuitry to ensure that there is no shoot-through in directly driven external power MOSFETs.
The timing of the start-up sequence is determined by the selection of three timing capacitors.
This allows optimization for a wide range of motors and loads.
• • Block Diagram 17 VDD 750nA FB A 22 FB B 23 FB C 24 BACK EMF SAMPLER 500nA VOLTAGE CONTROLLED OSCILLATOR 1.
5V – + CAT 750nA VDD 19 CRT – 21 CRR 20 SPEED CVCO FB 15 16 RVCO 1.
5V + VDD VCO/TACH 13 VCO OUT VCO OUT R A F B + COMMUTATION STATE MACHINE HA HB GATING LOGIC & OUTPUT DRIVERS UVLO HC LA LB LC UV FAULT 4kΩ REFERENCE 2 3 4 9 10 11 18 8 SPEED SET 5 SPEED COMP – 3.
9V – + E D C 1.
7V CT 6 20kHz ISENSE 1 ILIMIT 12 8kΩ CIOS 26 25 BRAKE 1.
7V ×5 VREF 16kΩ – + – ILIMIT 1-SHOT 1.
4V VDD + VDD 14 28 GND 27 RREF 7 VREF REV.
1.
0.
2 7/2/01 ML4425 PRO...


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