Datasheet OQ8844 Datasheet (Philips)

INTEGRATED CIRCUITS

DATA SH EET

OQ8844

Digital Servo Driver (DSD-2)

Product specification
File under Integrated Circuits, IC01

1995 Nov 27

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

FEATURES
Servo functions

• 1-bit class-D focus actuator driver (3.3 Ω)

• 1-bit class-D radial actuator driver (3.7 Ω)

• 1-bit class-D sledge motor driver (2.5 Ω).

GENERAL DESCRIPTION

The OQ8844 or Digital Servo Driver 2 (DSD2) consists of
1-bit class-D power drivers, which are specially designed
for digital servo applications. Three such amplifiers are
integrated in one chip, to drive the focus and radial
actuators and the sledge motor of a compact disc optical
system.

Other features

• Supply voltage 5 V only

• Small package (SOT163-1)

• Higher efficiency, compared with conventional drivers,

due to the class-D principle

• Built-in digital notch filters for higher efficiency

The main benefits of using this principle are its higher
efficiency grade compared to conventional analog power
amplifiers, its higher integration level, its differential output
and the fact that only a few external components are
needed. When using these digital power drivers in a digital
servo application, the statement ‘complete digital servo
loop’ becomes more realistic.

• Enable input for focus and radial driver

• Enable input for sledge driver

• Differential outputs for all drivers

• Separate power supply pins for all drivers.

QUICK REFERENCE DATA

SYMBOL PARAMETER MIN. TYP. MAX. UNIT

V

DDD

V

DD(F)

V

DD(R)

V

DD(S)

I

DDDq

I

DD(F)

I

DD(R)

I

DD(S)

f

i(clk)

P

tot

T

amb

digital supply voltage 4.5 − 5.5 V
supply voltage focus actuator 4.5 − 5.5 V
supply voltage radial actuator 4.5 − 5.5 V
supply voltage sledge actuator 4.5 − 5.5 V
quiescent supply current digital part −−10 µA
supply current focus − 126 250 mA
supply current radial − 20 250 mA
supply current sledge − 150 560 mA
input clock frequency − 4.2336 5 MHz
total power dissipation − 110 − mW
operating ambient temperature −40 − +85 °C

ORDERING INFORMATION

TYPE

NUMBER

NAME DESCRIPTION VERSION

PACKAGE

OQ8844 SO20 plastic small outline package; 20 leads; body width 7.5 mm SOT163-1

1995 Nov 27 2

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

BLOCK DIAGRAM

RAC

FOC

SLC

CLI

EN1
EN2

4

3

2

7
8

9

OQ8844

CONTROL

V

V

V

DD(R)

DDD

613141

DIGITAL

NOTCH FILTER

DIGITAL

NOTCH FILTER

DIGITAL

NOTCH FILTER

5101718

V

SS(R)

SSD

V

DD(F)

V

SS(F)

V

DD(S)

ENDSTAGE

H−BRIDGE

ENDSTAGE

H−BRIDGE

ENDSTAGE

H−BRIDGE

V

SSS

11
12

15
16

19
20

MBG785

RA+
RA−

FO+
FO−

SL+
SL−

Fig.1 Block diagram.

1995 Nov 27 3

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

PINNING

SYMBOL PIN DESCRIPTION

V

DD(S)

SLC 2 PDM input for sledge driver
FOC 3 PDM input for focus driver
RAC 4 PDM input for radial driver
V

SSD

V

DDD

CLI 7 clock input
EN1 8 enable input 1
EN2 9 enable input 2
V

SS(R)

RA+ 11 radial driver (positive output)
RA− 12 radial driver (negative output)
V

DD(R)

V

DD(F)

FO+ 15 focus driver (positive output)
FO− 16 focus driver (negative output)
V

SS(F)

V

SSS

SL+ 19 sledge driver (positive output)
SL− 20 sledge driver (negative output)

supply voltage for sledge motor

1

driver

5 digital ground
6 digital supply voltage

10 radial driver ground

13 radial supply voltage
14 focus supply voltage

17 focus ground
18 sledge driver ground

handbook, halfpage

V

V

1

DD(S)

2

SLC

FOC

3

RAC

4

V

5

SSD

V

DDD

CLI
EN1
EN2 RA−

SS(R)

6
7
8
9

10

OQ8844

MBG784

Fig.2 Pin configuration.

20

SL−
SL+

19

V

18

SSS

V

17

SS(F)

16

FO−

15

FO+
V

14

DD(F)

V

13

DD(R)

12
11

RA+

1995 Nov 27 4

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

FUNCTIONAL DESCRIPTION
Principle of a class-D digital power driver

Figure 3 shows the block diagram of one of the digital
drivers integrated in the DSD2. It consists of a timing block
and four CMOS switches. The input signal is a 1-bit Pulse
Density Modulated (PDM) signal, the output of the digital
servo ICs.

The maximum operating clock frequency of the device is
5 MHz. With the mentioned digital servo ICs, the operating
frequency of the digital drivers is 4.2336 MHz
(96 × 44.1 kHz). The sampling frequency of the 1-bit code
however is 1.0584 MHz, so internally in the DSD2 the
clock speed of the switches will be 1.0584 MHz.
The higher input clock frequency is used to make
non-overlapping pulses to prevent short-circuits between
the supply voltages. For the control of the switches, two
states can be distinguished. If the 1-bit code contains a
logic 1, switches A and D are closed and current will flow
in the direction as shown in Fig.4.

If the 1-bit code contains a logic 0, switches B and C are
closed and current will flow in the opposite direction, as
shown in Fig.5.

This indicates that the difference between the mean
number of ones and zeros in the PDM signal determines
the direction in which the actuator or motor will rotate.

half the sample frequency of 1.0584 MHz. This results in a
high dissipation and the motor does not move.

To improve the efficiency, a digital notch filter is added at
the input of the digital drivers. This filters the Idle mode
pattern (1010101010 etc.) see Fig.6.

The amplitude transfer as a function of frequency is given
in Fig.7.

Figure 7 shows that the filter has a zero on
consequentially filtering out the idle pattern (101010).
The output of this filter is a three-level code (1.5-bit).
For the control of the switches three states (1.5-bit) can be
distinguished: the two states as described earlier and a
third one. This state is used when an idling pattern is
supplied.

Switches C and D are closed (see Fig.8). In this idle mode,
no current will flow and thus the efficiency will be improved.
This mode is also used to short-circuit the inductive
actuator/motor. In this way, high induction voltages are
prevented because the current can commutate via the
filter and the short-circuit in the switches. All three drivers
(radial, focus and sledge) contain a digital notch filter as
described. Each driver has its own power supply pins to
reduce crosstalk because of the relative high current
flowing through the pins.

1

⁄2fs,

If the mean number of ones and zeros is equal (Idle mode)
the current through the motor or actuator is alternated
between the positive and negative direction at a speed of

1995 Nov 27 5

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

1-bit

code

TIMING

clock

MBG786

(1) Sledge motor; focus/radial motor.

Fig.3 One of the digital drivers.

V

DD

1-bit

code

(1)

M

V

SS

'1'

TIMING

clock

MBG787

(1) Sledge motor; focus/radial motor.

V

DD

I

pos

AB

(1)

M

CD

V

SS

Fig.4 1-bit code is logic 1.

V

DD

I

neg

1-bit

code

'0'

TIMING

clock

MBG788

(1) Sledge motor; focus/radial motor.

AB

(1)

M

CD

V

SS

Fig.5 1-bit code is logic 0.

1995 Nov 27 6

1-bit 1.5-bit

The filter consists of a simple delay element (flip-flop) and an adder.
The transfer from input-to-output is: H(z) =1 + z

1/Z

MBG789

−1

.

Fig.6 Notch filter at input of digital drivers.

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

|H|

MBG790

1/2f

s

Fig.7 Amplitude transfer.

Switches

The digital part of the power drivers consists of standard
cells. The power switches are specifically designed for CD
applications. The most important feature is their
on-resistance. In the applications, they have to drive very
low-ohmic actuators and/or motors. The switches are
designed to have an on-resistance of 2 Ω for the actuator
drivers and 1 Ω for the sledge motor driver. In any mode,
there are always two switches in series with the
actuator/motor. The total loss due to the switches is 4 Ω for
the actuators and 2 Ω for the sledge motor.

Timing of input and output signals

All internal timing signals are derived from the externally
supplied CLI signal.

V

DD

1-bit

code

'idle'

TIMING

clock

MBG791

(1) Sledge motor; focus/radial motor.

AB

(1)

M

CD

I

idle

V

SS

Fig.8 Idling pattern.

The switching of the outputs occurs in a similar way,
except that in this event the negative edge of CLI is used.
In this way, the input signals are immune to the noise
radiated by the switching of the outputs. It is possible that
an output transition will have a noticeable effect on the
power supply voltage or the ground voltage. To avoid
simultaneous transitions of all outputs, the outputs of each
bridge are also clocked at a different phase of CLI.
Consequentially there are only 3 out of 4 negative edges
effective.

To reset the circuit, both the reset condition and the clock
should be present, because all flip-flops are reset
synchronously. The clock signal is also required to obtain
one of the possible modes of operation indicated in
Table 1.

Sampling of the data inputs (SLC, FOC and RAC) occurs
at a frequency of

1

⁄4CL. For each channel, the clocking-in

occurs at a different positive edge of CLI. Because there
are only 3 channels, and the clock frequency CLI is
divided-by-4, only 3 out of 4 positive edges are effective for
sampling one of the inputs.

1995 Nov 27 7

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

Table 1 Possible modes of operation

EN1 EN2 SLEDGE DRIVER

FOCUS/RADIAL

DRIVER

0 0 off off standby
0 1 off on partly operating
1 0 off off reset
1 1 on on operating

The timing diagram as shown in Fig.9 gives the relation between the different clocks.
The negative edge of the signals called nc10 to nc12 is used to process the incoming data (see Table 2).
The negative edge of all signals called c10s to c12s is used to trigger the outputs (see Table 2).

Table 2 Signals nc10 to nc12 and c10s to c12s

SIGNAL DESCRIPTION

ncl0 sledge input sampling clock
ncl1 focus input sampling clock
ncl2 radial input sampling clock

cl0s sledge output trigger clock
cl1s focus output trigger clock
cl2s radial output trigger clock

MODE

LIMITING VALUES

In accordance with the Absolute Maximum Rating System (IEC 134).

SYMBOL PARAMETER MIN. MAX. UNIT

V

DDD

V

DDA

V

− V

SSD

P

tot

T

stg

T

amb

SSA

digital supply voltage −0.5 +6.5 V
analog supply voltage −0.5 +6.5 V
ground supply voltage difference −5+5mV
total power dissipation − 730 mW
storage temperature −55 +150 °C
operating ambient temperature −40 +85 °C

THERMAL CHARACTERISTICS

SYMBOL PARAMETER VALUE UNIT

R

th j-a

thermal resistance from junction to ambient in free air 75 K/W

1995 Nov 27 8

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

CHARACTERISTICS

V

DDD=VDDA

SYMBOL PARAMETER CONDITIONS MIN. TYP. MAX. UNIT

V

DDD

V

DDA

I

DDDq

I

DD(F)max

I

DD(R)max

I

DD(S)max

f

i(clk)

P

tot

T

amb

Digital inputs; SLC, FOC, RAC, CLI, EN1 and EN2

V

IL

V

IH

I

LI

Clock input; CLI

f

clk

Analog outputs; FO+ and FO−

I

O

R

O

Analog outputs; RA+ and RA−

I

O

R

O

Analog outputs; SL+ and SL−

I

O

R

O

=5V; V

SSD=VSSA

=0V; T

=25°C; unless otherwise specified.

amb

supply voltage digital part 4.5 − 5.5 V
supply voltage analog part 4.5 − 5.5 V
quiescent supply current digital

−−10 µA

part
maximum supply current focus note 1 − 126 250 mA
maximum supply current radial note 1 − 20 250 mA
maximum supply current sledge note 1 − 150 560 mA
input clock frequency − 4.2336 5 MHz
totalpower dissipation − 110 − mW
operating ambient temperature −40 − +85 °C

LOW level input voltage T
HIGH level input voltage T

= −40 to 85 °C −−0.2V

amb

= −40 to 85 °C 0.8V

amb

DDD

−− V

DDD

V

input leakage current −−1µA

clock frequency − 4.2336 5 MHz

output current −−250 mA
output resistance note 2 − 3.3 4.1 Ω

output current −−250 mA
output resistance note 2 − 3.7 4.6 Ω

output current −−560 mA
output resistance note 2 − 2.5 3.1 Ω

Notes

V

DDA max

1. Maximum supply current depends on the value of R

L

=

:

I

max

---------------------------­RORL+()

2. Output resistance is defined as the series resistance of the complete bridge.

1995 Nov 27 9

1995 Nov 27 10

inputs

outputs

full pagewidth

MBG792

CLI

SLC

FOC

RAC

ncI0

ncI1

ncI2

cI0s

cI1s

cI2s

SL+

SL−

FO+

FO−

RA+

RA−

Timing diagram

Digital Servo Driver (DSD-2) OQ8844

Philips Semiconductors Product specification

Sampling of the incoming data is marked by a ‘∗’.

Fig.9 Timing diagram.

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

PACKAGE OUTLINE

SO20: plastic small outline package; 20 leads; body width 7.5 mm

D

c

y

Z

20

pin 1 index

1

e

11

A

2

10

w M

b

p

SOT163-1

E

H

E

Q

A

1

L

p

L

detail X

(A )

A

X

v M

A

A

3

θ

0 5 10 mm

scale

DIMENSIONS (inch dimensions are derived from the original mm dimensions)

mm

OUTLINE
VERSION

SOT163-1

A

max.

2.65

0.10

A

1

0.30

0.10

0.012

0.004

A2A

2.45

2.25

0.096

0.089

IEC JEDEC EIAJ

075E04 MS-013AC

0.25

0.01

b

3

p

0.49

0.32

0.36

0.23

0.019

0.013

0.014

0.009

UNIT

inches

Note

1. Plastic or metal protrusions of 0.15 mm maximum per side are not included.

(1)E(1) (1)

cD

13.0

7.6

7.4

0.30

0.29

1.27

0.050

12.6

0.51

0.49

REFERENCES

1995 Nov 27 11

eHELLpQ

10.65

10.00

0.419

0.394

1.4

0.055

1.1

0.4

0.043

0.016

1.1

1.0

0.043

0.039

PROJECTION

0.25

0.25 0.1

0.01

0.01

EUROPEAN

ywv θ

Z

0.9

0.4

0.035

0.004

0.016

ISSUE DATE

95-01-24
97-05-22

o

8

o

0

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

SOLDERING
Introduction

There is no soldering method that is ideal for all IC
packages. Wave soldering is often preferred when
through-hole and surface mounted components are mixed
on one printed-circuit board. However, wave soldering is
not always suitable for surface mounted ICs, or for
printed-circuits with high population densities. In these
situations reflow soldering is often used.

This text gives a very brief insight to a complex technology.
A more in-depth account of soldering ICs can be found in
our

“IC Package Databook”

Reflow soldering

Reflow soldering techniques are suitable for all SO
packages.

Reflow soldering requires solder paste (a suspension of
fine solder particles, flux and binding agent) to be applied
to the printed-circuit board by screen printing, stencilling or
pressure-syringe dispensing before package placement.

Several techniques exist for reflowing; for example,
thermal conduction by heated belt. Dwell times vary
between 50 and 300 seconds depending on heating
method. Typical reflow temperatures range from
215 to 250 °C.

Preheating is necessary to dry the paste and evaporate
the binding agent. Preheating duration: 45 minutes at
45 °C.

(order code 9398 652 90011).

Wave soldering

Wave soldering techniques can be used for all SO
packages if the following conditions are observed:

• A double-wave (a turbulent wave with high upward
pressure followed by a smooth laminar wave) soldering
technique should be used.

• The longitudinal axis of the package footprint must be
parallel to the solder flow.

• The package footprint must incorporate solder thieves at
the downstream end.

During placement and before soldering, the package must
be fixed with a droplet of adhesive. The adhesive can be
applied by screen printing, pin transfer or syringe
dispensing. The package can be soldered after the
adhesive is cured.

Maximum permissible solder temperature is 260 °C, and
maximum duration of package immersion in solder is
10 seconds, if cooled to less than 150 °C within
6 seconds. Typical dwell time is 4 seconds at 250 °C.

A mildly-activated flux will eliminate the need for removal
of corrosive residues in most applications.

Repairing soldered joints

Fix the component by first soldering two diagonally­opposite end leads. Use only a low voltage soldering iron
(less than 24 V) applied to the flat part of the lead. Contact
time must be limited to 10 seconds at up to 300 °C. When
using a dedicated tool, all other leads can be soldered in
one operation within 2 to 5 seconds between
270 and 320 °C.

1995 Nov 27 12

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

DEFINITIONS

Data sheet status

Objective specification This data sheet contains target or goal specifications for product development.
Preliminary specification This data sheet contains preliminary data; supplementary data may be published later.
Product specification This data sheet contains final product specifications.

Limiting values

Limiting values given are in accordance with the Absolute Maximum Rating System (IEC 134). Stress above one or
more of the limiting values may cause permanent damage to the device. These are stress ratings only and operation
of the device at these or at any other conditions above those given in the Characteristics sections of the specification
is not implied. Exposure to limiting values for extended periods may affect device reliability.

Application information

Where application information is given, it is advisory and does not form part of the specification.

LIFE SUPPORT APPLICATIONS

These products are not designed for use in life support appliances, devices, or systems where malfunction of these
products can reasonably be expected to result in personal injury. Philips customers using or selling these products for
use in such applications do so at their own risk and agree to fully indemnify Philips for any damages resulting from such
improper use or sale.

1995 Nov 27 13

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

NOTES

1995 Nov 27 14

Philips Semiconductors Product specification

Digital Servo Driver (DSD-2) OQ8844

NOTES

1995 Nov 27 15

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SCD45 © Philips Electronics N.V. 1995

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513061/50/01/pp16 Date of release: 1995 Nov 27
Document order number: 9397 750 00471