FAN8621B

11

Application Informations

General

The FAN8621B is a stand alone combination chip consisting of Spindle Motor (SPM) and Voice Coil Motor (VCM)circuit for

HDD applications. The speed control of SPM is achieved by internal Synchronous Phase Locked Loop (SPLL). The

FAN8621B supplies adjustable regulated power with external component and signals READY indicating SPM is locked

within some speed range (typically ±0.7% speed error). Current set point is applied by two PWM signals and VCM current is

monitored by external sense resistor. VCM circuit generates 4 voltage references for testing. Fig.1 shows overall interfacing of

FAN8621B with external and HDD motors

Figure 1. Overall Interfacing of the FAN8621B

The control signals have three status and their function is summarized as follows;

Table 1. Control PIN function

Notes:

1. SPM bias + SPM Output Driver enable

2. Makes SPM Open Loop (Start-up) Commutation Signal

3. Test Only when READY is low

Pin Status

Signals

HZ

L

CNTL1

SPM

bias enable

disable

Brake

disable

disable

enable

CNTL2

Commutation

hard

Hard

soft

Start Clock

-

CNTL3

VCM

enable

disable

disable

Retract

disable

disable

enable

GAINSEL

Start-up hold

normal

normal

Sense Amp gain

2

2

8

Power

Power

Power

Power

Management

Management

Management

Management

SPM

SPM

SPM

SPM

VCM

VCM

VCM

VCM

Retract/Brake

DIGITAL

DIGITAL

DIGITAL

DIGITAL

ASIC

ASIC

ASIC

ASIC

Interface

Interface

Interface

Interface

POR

CNTL1

CNTL2

CNTL3

PWMH

PWML

GAINSEL

READY

FG

VCMREF4V

Vreg3.3

RPMSEL

TSD

CLK