Philips tdf5242t DATASHEETS

INTEGRATED CIRCUITS

DATA SH EET

TDF5242T

Brushless DC motor drive circuit

Preliminary speciﬁcation Supersedes data of 1997 Apr 23 File under Integrated Circuits, IC11

1997 Sep 12

Philips Semiconductors Preliminary speciﬁcation

Brushless DC motor drive circuit TDF5242T

FEATURES

• Full-wave commutation without position sensors

• Built-in start-up circuitry

• Six outputs that can drive three external transistor pairs:

APPLICATIONS

• High-power applications, for instance: – high-end hard disk drives – automotive applications.

– output current 0.2 A (typ.) – low saturation voltage – built-in current limiter

• Thermal protection

• Tacho output without extra sensor

• Transconductance amplifier for an external control

transistor

• Brake control input

• Direction control input.

GENERAL DESCRIPTION

The TDF5242T is a bipolar integrated circuit for driving 3-phase brushless DC motors in full-wave mode. The device functions sensorless, thus saving 3 hall-effect sensors, using the back-EMF (Electro Motive Force) sensing technique to sense the rotor position. It includes 6 pre-drivers able to control external FETs (Field Effect Transistors) or bipolar transistors. It offers brake and direction control. It is ideally suited for high-power applications such as high-end hard disk drives and automotive applications.

QUICK REFERENCE DATA

Measured over full voltage and temperature range.

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

VMOT

supply voltage note 1 4 − 18 V input voltage to the output

3 − 18 V

driver stages

LIM

driver output voltage IO= 100 mA; lower transistor −−0.35 V

= 100 mA; upper transistor 1.05 −−V

current limiting V

= 14.5 V; RO=47Ω 150 200 250 mA

VMOT

Note

1. An unstabilized supply can be used.

ORDERING INFORMATION

TYPE

NUMBER

NUMBER DESCRIPTION VERSION

PACKAGE

TDF5242T SO28 plastic small outline package; 28 leads; body width 7.5 mm SOT136-1

1997 Sep 12 2

Philips Semiconductors Preliminary speciﬁcation

Brushless DC motor drive circuit TDF5242T

BLOCK DIAGRAM

handbook, full pagewidth

+AMP IN

−AMP IN

CAP-ST

CAP-DC CAP-CD

TEST

CAP-TI

19 20

15 14

THERMAL

PROTECTION

AMP OUT VMOT

START-UP

OSCILLATOR

ADAPTIVE

COMMUTATION

DELAY

TIMING

ROTATION

SPEED

AND

DETECTOR

OUTPUT

STAGE

21 6

TRANS-

CONDUCTANCE

AMPLIFIER

COMMUTATION

LOGIC

OUTPUT DRIVER STAGE

OUTPUT DRIVER

STAGE

OUTPUT DRIVER

STAGE

OUTPUT DRIVER

STAGE

OUTPUT DRIVER

STAGE

OUT-NA

OUT-PA

OUT-NB

OUT-PB

OUT-PC

DIRECTION

LOGIC

BRAKE

LOGIC

TDF5242T

12, 17, 25

n.c.

DIR BRAKE GND2 GND1 V

9113

Fig.1 Block diagram.

1997 Sep 12 3

EMF COMPARATORS

OUTPUT DRIVER

STAGE

24 26

MGG988

OUT-NC

COMP-A

COMP-B

COMP-C MOT0

Philips Semiconductors Preliminary speciﬁcation

Brushless DC motor drive circuit TDF5242T

PINNING

SYMBOL PIN DESCRIPTION

OUT-NB 1 driver output B for driving the

n-channel power FET or power NPN

OUT-PB 2 driver output B for driving the

p-channel power FET or power PNP

GND1 3 ground (0 V) motor supply return for

output stages

OUT-PC 4 driver output C for driving the

p-channel power FET or power PNP

OUT-NC 5 driver output C for driving the

n-channel power FET or power NPN

VMOT 6 input voltage for the output driver

stages DIR 7 direction input command TEST 8 test input/output BRAKE 9 brake input FG 10 frequency generator: output of the

rotation speed detector stage GND2 11 ground supply return for control

circuits n.c. 12 not connected V

13 supply voltage

CAP-CD 14 external capacitor connection for

adaptive communication delay timing CAP-DC 15 external capacitor connection for

adaptive communication delay

timing copy CAP-ST 16 external capacitor connection for

start-up oscillator n.c. 17 not connected CAP-TI 18 external capacitor connection for

timing +AMP IN 19 non-inverting input of the

transconductance ampliﬁer

−AMP IN 20 inverting input of the

transconductance ampliﬁer AMP OUT 21 transconductance ampliﬁer output

(open collector) COMP-A 22 comparator input corresponding to

output A

SYMBOL PIN DESCRIPTION

COMP-B 23 comparator input corresponding to

output B

COMP-C 24 comparator input corresponding to

output C n.c. 25 not connected MOT0 26 input from the star point of the motor

coils OUT-NA 27 driver output A for driving the

n-channel power FET or power NPN OUT-PA 28 driver output A for driving the

p-channel power FET or power PNP

handbook, halfpage

OUT-NB OUT-PB

GND1 OUT-PC OUT-NC

VMOT

DIR

TEST

BRAKE

GND2

n.c.

CAP-CD

1 2 3 4 5 6 7

TDA5242T

9 10 11 12 13

MGG987

28 27 26 25 24 23 22 21 20 19 18 17 16 1514

OUT-PA OUT-NA MOT0 n.c. COMP-C COMP-B COMP-A AMP OUT

−AMP IN +AMP IN

CAP-TI n.c. CAP-ST CAP-DC

Fig.2 Pin configuration.

1997 Sep 12 4

Philips Semiconductors Preliminary speciﬁcation

Brushless DC motor drive circuit TDF5242T

FUNCTIONAL DESCRIPTION Introduction

Full-wave driving of a three phase motor requires three push-pull output stages. In each of the six possible states two outputs are active, one sourcing (H) and one sinking (L). The third output presents a high impedance (Z) to the motor, which enables measurement of the motor back-EMF (Electro Motive Force) in the corresponding motor coil by the EMF comparator at each output. The commutation logic is responsible for control of the output transistors and selection of the correct EMF comparator. In Table 1, the six possible states of the externally connected output transistors have been depicted and the corresponding output levels on the NA, PA, NB, PB, NC and PC outputs of the TDF5242T.

The zero-crossing in the motor EMF (detected by the comparator selected by the commutation logic) is used to calculate the correct moment for the next commutation, that is, the change to the next output state. The delay is calculated (depending on the motor loading) by the adaptive commutation delay block.

The output stages are protected by a current limiting circuit and by thermal protection.

The detected zero-crossings are used to provide speed information. The information has been made available on the FG output pin. This output provides an output signal with a frequency equal to the commutation frequency.

The system will only function when the EMF voltage from the motor is present. Therefore, a start oscillator is provided that will generate commutation pulses when no zero-crossings in the motor voltage are available.

A timing function is incorporated into the device for internal timing and for timing of the reverse rotation detection.

The TDF5242T also contains an uncommitted transconductance amplifier (OTA) that can be used as a control amplifier. The output is capable of directly driving an external power transistor.

The TDF5242T is designed for systems with low current consumption. It uses I the output transistors (patented).

Start-up and commutation control

The system has been designed in such a way that the tolerances of the application components are not critical. However, the approximate values of the following components must still be determined:

• The start capacitor; this determines the frequency of the start oscillator

• The two capacitors in the adaptive commutation delay circuit; these are important in determining the optimum moment for commutation, depending on the type and loading of the motor

• The timing capacitor; this provides the system with its timing signals.

L logic and adaptive base drive for

Table 1 Output states (note 1)

DIR STATE MOT1 OUT-NA OUT-PA MOT2 OUT-NB OUT-PB MOT3 OUT-NC OUT-PC

H1ZLHLHHHLL H2HLLLHHZLH H3HLLZLHLHH H4ZLHHLLLHH H5LHHHLLZLH H6LHHZLHHLL

L1ZLHLHHHLL L2LHHZLHHLL L3LHHHLLZLH L4ZLHHLLLHH L5HLLZLHLHH L6HLLLHHZLH

Note

1. H = HIGH state; L = LOW state; Z = high-impedance OFF-state.

1997 Sep 12 5

Philips Semiconductors Preliminary speciﬁcation

Brushless DC motor drive circuit TDF5242T

START CAPACITOR (CAP-ST) This capacitor determines the frequency of the start

oscillator. It is charged and discharged, with a current of 2 µA, from 0.05 to 2.2 V and back to 0.05 V. The time to complete one cycle is:

start

2.15 C×()s (with C in µF )=

(1)

The start oscillator is reset by a commutation pulse and is only active when the system is in the start-up mode. A pulse from the start oscillator will cause the outputs to change to the next state. If the movement of the motor generates enough EMF, the TDF5242T will run the motor. If the amount of EMF generated is insufficient, then the motor will move one step only and will oscillate in its new position. The amplitude of the oscillation must decrease sufficiently before the arrival of the next start pulse, to prevent the pulse arriving during the wrong phase of the oscillation. The start capacitor should be chosen to meet this requirement.

The oscillation frequency of the motor is given by:

osc

---------------------------------- K

I× p×

2π

---------------------- -

where:

= torque constant (Nm/A)

I = current (A) p = number of magnetic pole-pairs J = inertia J (kg.m2).

Example: J = 72 × 10−6kg.m2, K=25×10−3Nm/A,p=6 and I = 0.5 A; this gives f

= 5 Hz. If the damping is high,

osc

a start frequency of 2 Hz can be chosen or t = 500 ms, thus, according to equation (1): C = 0.5/2.15 = 0.23 µF (choose 220 nF).

DAPTIVE COMMUTATION DELAY (CAP-CD AND CAP-DC)

In this circuit the capacitor CAP-CD is charged during one commutation period, with an interruption of the charging current during the diode pulse. During the next commutation period the capacitor is discharged at twice the charging current. The charging current is 8.1 µA and the discharging current 16.2 µA; the voltage range is from

0.9 to 2.2 V. The voltage must stay within this range at the lowest commutation frequency of interest, f

f 1.3×

6–

6231

------------ f

(C in nF)

8.1 10

--------------------------

If the commutation frequency is lower, a constant commutation delay after the zero-crossing is generated by the discharge from 2.2 down to 0.9 V at 16.2 µA; maximum delay = (0.076 × C) ms (with C in nF)

Example: nominal commutation frequency = 900 Hz and the lowest usable frequency = 400 Hz; so:

CAP-CD

6231

------------ 400

(choose 18 nF)

15.6==

The other capacitor, CAP-DC, is used to repeat the same delay by charging and discharging with 15.5 µA. The same value can be chosen as for CAP-CD. Figure 3 illustrates typical voltage waveforms.

handbook, full pagewidth

voltage

on CAP-CD

(1)

(1) COM = commutation. (2) ZCR = zero-crossing.

voltage

on CAP-DC

COMCOM

(2)

ZCRZCR

COM COM COM COM

ZCR ZCR ZCR ZCR

Fig.3 CAP-CD and CAP-DC typical voltage waveforms in normal running mode.

1997 Sep 12 6

= V

max

MGG993

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