LV8212T

No.A0817-10/13

LV8212T Functional Description and External Components

This document presents information necessary to design systems with the best possible characteristics and should be read

before designing driver circuits using the LV8212T.

1. Output Drive Circuits and Speed Control Methods

The LV8212T adopts a synchronous commutation direct PWM drive method to minimize power loss in the output.

Low on-resistance DMOS devices are used as the output transistors. (the upper and lower side output block devices

on-resistance is 0.5

Ω (typical)).

The LV8212T spindle drivers control system takes an analog input and uses a V-type control amplifier.

The gain of V-type control circuit can be selected by the following formula with the GSW pin (pin 54).

typ = 0.34V/V (when the GSW pin is low)

and typ = 0.17V/V (when the GSW pin is high).

The V-type control amplifier based speed control system controls the speed by controlling the voltage of the VCTL

pin (pin 16) and SREF pin (pin 20). The circuit provides forward torque when VCTL is greater than VCREF, and

allows the application to select either reverse torque braking (when the BRK pin is low) or short-circuit braking (when

the BRK pin is low) when VCTL is less than VCREF. The PWM frequency is twice the frequency of the charge pump

pulse rate (pin 57).

2. Soft Switching Circuit

This IC performs “soft switching”, which is a technique that varies the duty and achieves quieter motor operation by

reducing the level of motor drive noise. This IC provides a “current application ON/OFF dual sided soft switching”

type soft switching function.

3. Current Limiter Circuit

The current limit value of the current limiter circuit is determined by RF in the equation I = VRF/Rf (here, VRF =

0.20V, typical).

Spindle block : the current limiter circuit detects the SPGND pin (pin 1, 6 and 8) peak current at the SPRF pin (pin 5)

and turns the sink side transistor off.

4. OSC circuit

The OSC pin (pin 17) is an oscillation terminal for start-up current commutation of sensor-less, it has two types, the

main-clock dividing mode, and the self-excited oscillation mode. The main-clock dividing mode can be set-up by

connecting the OSC pin to the VCC pin or GND. The set-up frequency is divided by internal oscillation frequency

(here, 3.2 MHz as typical). And, when the OSC pin is connected to the VCC pin (high level), the main-clock divided

by 4096 to get ground 781Hz.

Also, when the OSC pin is connected to GND, the main-clock is divided by 3072 to get around 1042Hz.

The self-excited oscillation mode can be set up by connecting a capacitor between the OSC pin and GND.

When the self-excited oscillation mode is chosen, the OSC pin starts self-excited.

Thus, it becomes set-up frequency. Oscillation frequency can be adjusted by changing the capacity of an external

capacitor. (ex, if capacity is made small, the set-up frequency will become high.)

When the OSC pin is connected to the VCC pin or GND, and if there is no problem in the start-up characteristic, the

number of external components are reduced. However, if a problem occurs in it, you should choose the value of a

capacitor which can obtain the best start-up characteristic after choosing self-excited mode.

5. Spindle Block Position Sensor comparator Circuit

The spindle block position sensor comparator circuit uses the back EMF signal generated by motor rotation to detect

the rotor position. The output block power application timing is determined based on the position information

acquired by this circuit. Start-up problems due to noise on the comparator inputs can be ameliorated by inserting a

capacitor (1000 of 4700pF) between the SPCIN pin (pin 14) and the SPFIL pin (pin 15).

6. Actuator Block (channel 4 and 5) Output Drive Circuit and Speed Control Method

This IC adopts a synchronous commutation direct PWM drive method. Low on-resistance DMOS devices are used as

the output transistors. (the upper and lower side output block devices on-resistance is 1.3

Ω (typical)).

This circuit takes an analog input and uses a V-type control amplifier. The V-type control amplifier based speed

control system controls the speed by controlling the voltage of the IN4 pin (pin 23 : channel 4), the IN5 pin (pin 22 :

channel 5) and the AREF pin (pin 21).