MTD6505T-E/NA(2011) View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

MTD6505T-E/NA
(Rev.:2011)

Sinusoidal Sensorless 3-Phase Brushless DC Fan Motor Driver

Microchip Technology 

MTD6505

4.7 Internal Voltage Regulator

VBIAS voltage is generated internally and is used to

supply internal logical blocks. The VBIAS pin is used to

connect an external decoupling capacitor (1 µF or

higher). Notice that this pin is for IC internal use, and is

not designed to supply DC current to external blocks.

4.8 BEMF Coefficient Setting

Km is the electro-mechanical coupling coefficient of the

motor (also referred to as “motor constant” or “BEMF

constant”). Depending on the conventions in use, the

exact definition of Km and its measurement criteria can

vary among motor manufacturers. To accommodate

various motor applications, the MTD6505 provides

options to facilitate diverse BEMF coefficients.

The MTD6505 defines BEMF coefficient (Km) as the

peak value of the phase-to-phase BEMF voltage,

normalized to the electrical speed of the motor. The

following table offers methods to set the Km value for

the MTD6505 device.

TABLE 4-2: Km SETTINGS

Km

Option

Km (mV/Hz) Range

Phase-to-Phase

Min

Max

RPROG

Km0

3.25

6.5

GND

Km1

6.5

13

24 k

Km2

13

26

3.9 k

Km3

26

52

VBIAS

The RPROG sensing is actually a sequence that is con-

trolled by the firmware. For any given RPROG, the inter-

nal control block will output the corresponding Km

range.

DS22281A-page 10

 2011 Microchip Technology Inc.

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