wolfson WM2629 User Manual

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WM2629

Octal 8-bit, Serial Input, Vol t age Output DAC

with Power Down

Production Data, April 2001, Rev 1.0

FEATURES

• Eight 8-bit DACs in one package

• Dual supply 2.7V to 5.5V operation

• DNL ±0.1 LSBs, INL ±0. 3 LS Bs typical

• Programmable settling time / power
(1.0µs typical in fast mode)

• Microcontroller compatible serial interface

• Power down mode ( < 0.1µA)

• Monotonic over temperature

• Data output for daisy chaining

APPLICATIONS

• Battery powered test instruments

• Digital offset and gain adjustment

• Battery operated / remote industrial controls

• Programmable loop controllers

• CNC machine tools

• Machine and motion control devices

• Wireless telephone and communication systems

• Robotics

ORDERING INFORMATION

DEVICE TEMP. RANGE PACKAGE

WM2629CDT 0° to 70°C 20-pin TSSOP

WM2629IDT -40° to 85°C 20-pin TSSOP

DESCRIPTION

The WM2629 is an octal, 8-bit, resistor string digital-to-anal ogue
converter. The eight individual DACs contai ned in the IC c an be
switched in pairs between fast and sl ow (low power) operation
modes, or powered down, under software control. Alternatively,
the whole device can be powered down, reducing current
consumption to les s than 0.1µA.

The DAC outputs are buffered by a rail -to-rail amplifier with a
gain of two, which is configurable as Class A (fast mode) or
Class AB (for low-power mode).

The WM2629 has been designed to interfac e direc tl y to indus try
standard microprocess ors and DSPs, and can operate on two
separate analogue and digital power supplies. It is program med
with a 16-bit serial word comprising 4 address bits and up to 12
DAC or control register data bits. All eight DACs can be
simultaneously forced to a preset value using a preset input pin.

A daisy-chain data output mak es i t pos sibl e to c ontrol several of
Wolfson’s octal DACs from the same interface, without
increasing the number of c ontrol lines.

The device is available in a 20-pin TSSOP package.
Commercial temperature (0° to 70°C) and Industrial
temperature (-40° to 85°C) variants are supported.

BLOCK DIAGRAM TYPICAL PERFORMANCE

AVDD

REF
(16)

DAC A

DIN (2)

SCLK (3)

FS (4)

MODE (17)

PREB (5)

DOUT (19)

SERIAL

INTERFACE

AND

CONTROL

LOGIC

LATCH

DACs B, C, D, E, F, G, H

LOADB

(18)

RESISTOR

POWER/SPEED

CONTROL

VREF/2

as DAC A

STRING

WOLFSON MICROELECTRONICS LTD

Bernard Terrace, Edinburgh, EH8 9NX, UK
Tel: [phone]
Fax: [phone]
Email: [e-mail]
www.wolfsonmicro.com

(11)

AGND

(10)

DVDD

(20)

DGND

(1)

(12) OUT A

(6-9, 13-15)
OUT B to H

0.04

0.03

0.02

0.01

0

-0.01

-0.02

Differential Non-Linearity (LSBs)

-0.03

-0.04
0 32 64 96 128 160 192 224 256

DIGITAL CODE

Production Data datasheets contain final

specifications current on publication date.

Supply of products conforms to Wol fson
Microelectronics’ Term s and Conditions.

2001 Wolfson Microelectronics Ltd.

WM2629 Production Data
PIN CONFIGURATION

20

DGND

DIN

SCLK

PREB
OUTE
OUTF

OUTG

OUTH
AGND

1
2
3

FS

4
5
6
7
8

9
10

DVDD

19

DOUT

18

LOADB

17

MODE

16

REF

15

OUTD

14

OUTC

13

OUTB

12
11

OUTA
AVDD

PIN DESCRIPTION

PIN NO NAME TYPE DESCRIPTION

1
2
3
4
5
6
7
8

9
10
11
12
13
14
15
16
17
18
19
20

DGND Supply Digital Ground

DIN Digital input Digital serial data input

SCLK Digital input Serial clock input

FS Digital input Frame sync input

PREB Digital input Preset input

OUTE Analogue output DAC Output E

OUTF Analogue output DAC Output F
OUTG Analogue output DAC Output G
OUTH Analogue output DAC Output H
AGND Supply Analogue Ground
AVDD Supply Analogue positive power supply
OUTA Analogue output DAC Output A
OUTB Analogue output DAC Output B
OUTC Analogue output DAC Output C
OUTD Analogue output DAC Output D

REF Analogue I/O Voltage reference input / output

MODE Digital input Input mode

LOADB Digital input Load DAC

DOUT Digital output Serial data output
DVDD Supply Digital positive power supply

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Production Data WM2629

ABSOLUTE MAXIMUM RATINGS

Absolute Maximum Ratings are stress ratings only. Perm anent damage t o the devi ce m ay be c aused by c ont inuousl y operating at
or beyond these limits. Device f unctional operating limits and guaranteed performance specific ations are given under Electrical
Characteristics at the test conditions s pecified.

ESD Sensitive Device. Thi s device i s m anufactured on a CMOS proc ess. It is therefore generic ally sus ceptibl e
to damage from excessive static voltages . Proper ESD precaut ions m ust be t aken during handling and s torage
of this device.

CONDITION MIN MAX

Digital supply voltages, AVDD or DVDD to GND
Reference voltage
Digital input voltage range to GND
Operating temperature range, T

A

WM2629CDT
WM2629IDT

Storage temperature
Soldering temperature, 1.6mm (1/16 inch) from package body for 10

-0.3V AVDD + 0.3V

-0.3V DVDD + 0.3V
0°C

-40°C

-65°C 150°C

7V

70°C
85°C

260°C

seconds

RECOMMENDED OPERATING CONDITIONS

PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT

Supply voltage

High-level digital input voltage
Low-level digital input voltage
Reference voltage to REF

Output Load Resistance
Load capacitance

Operating free-air temperature

AVDD,

DVDD

V

IH

V

IL

V

REF

R

L

C

L

T

A

2.7 5.5 V

2V

0.8 V
AVDD = 5V GND 4.096 AVDD
AVDD = 3V GND 2.048 AVDD V

2kΩ

100 pF

WM2629CDT 0 70 °C

WM2629IDT -40 85 °C

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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WM2629 Production Data
ELECTRICAL CHARACTERISTICS

Test Characteristics:

Over recommended operating condi tions (unless noted otherwise).

PARAMETER SYMBOL
Static DAC Specifications

Resolution
Integral non-linearity
Differential non-linearity
Zero code error
Gain error
DC power supply rejection ratio

INL Code 6 to 255 (see Note 1) ±0.3 ±1 LSB
DNL Code 6 to 255 (see Note 2) ±0.1 ±1 LSB
ZCE See Note 3 ±30 mV

GE See Note 4 ±0.6 % FS R

PSRR See Note 5 -60 dB

Zero code error temperature
coefficient

Gain error temperature coefficient

DAC Output Specifications

Output voltage range
Output load regulation

Power Supplies

Active supply current

IDD No load, V

Power down supply current

Dynamic DAC Specifications

Slew rate

Settling time

Glitch energy
Channel Crosstalk

Reference Input

Reference input resistanc e
Reference input capacitanc e

R

REF

C

REF

Reference feedthrough

Reference input bandwidth

TEST

CONDITIONS

MIN TYP MAX UNIT

8bits

See Note 6 30 µV/°C

See Note 6 10 ppm/°C

10kΩ Load 0 AVDD-0.4 V

2kΩ to 10kΩ load

See Note 7

=DVDD, VIL=0V

IH

±0.3 % Full

Scale

AVDD = DVDD = 5V,

V

= 2.048V

REF

Slow

Fast

16

6

21

8

mA
mA

See Note 8

No load, all inputs 0V

0.1 µA

or DVDD

DAC code 10%-90%
Load = 10kΩ, 100pF

Fast

Slow

4
1

10

V/µs

3

V/µs

See Note 9
DAC code 10%-90%
Load = 10kΩ, 100pF

Fast

Slow

1
3

3
7

µs
µs

See Note 10

Code 127 to code 128 4 nV-s

10kHz sine wave, 4V pk-pk -90 dB

100 kΩ

5pF

V

=2VPP at 1kHz

REF

-84 dB

+ 2.048V DC, DAC code 0

V

= 0.4VPP + 2.048V DC,

REF

DAC code 128

Slow

Fast

1.9

2.2

MHz
MHz

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Production Data WM2629

Test Characteristics:
Over recommended operating condi tions (unless noted otherwise).

PARAMETER SYMBOL

TEST

CONDITIONS

MIN TYP MAX UNIT

Digital Inputs

High level input current
Low level input current
Input capacitance

I

IH

I

IL

C

I

Input voltage = DVDD 1 µA

Input voltage = 0V -1 µA

8pF

Digital Output

High level digital output volt age
Low level digital output voltage
Output voltage rise time

V

OH

V

OL

Load = 10kΩ 2.6 V
Load = 10kΩ 0.4 V

Load = 10kΩ, 20pF, includes

720ns

propagation delay

Notes:

1. Integral non-linearity (INL) is the m axim um deviation of the output from the line between zero and full scale excludi ng
the effects of zero c ode and full scale errors).

2. Differential non-linearity (DNL) is the difference between the measured and ideal 1LSB amplitude change
of any adjacent two codes. A guarantee of monotonicity means the output voltage changes in t he same
direction (or remains constant) as a change in digital i nput code.

3. Zero code error is the voltage output when the DAC input code i s zero.

4. Gain error is the deviation from the ideal full-scale output excluding the effec ts of zero code error.

5. Power supply rejection ratio is measured by varying AVDD from 4.5V to 5.5V and measuring the
proportion of this signal imposed on the zero code error and the gain error.

6. Zero code error and Gain error temperature coefficients are norm al i sed to full-scale voltage.

7. Output load regulation is the difference between the output voltage at full scale with a 10kΩ load and 2kΩ

load. It is expressed as a percent age of the full scale output vol tage with a 10kΩ load.

8. I

is measured while continuous l y writing code 128 to the DAC. For VIH < DVDD - 0.7V and VIL > 0.7V

DD

supply current will increase.

9. Slew rate results are for the lower value of the rising and falling edge s l ew rates.

10. Settling time is the time taken for the signal to settle to within 0. 5LS B of the final measured value for both rising and
falling edges. Limits are ensured by design and characterisation, but are not production tested.

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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WM2629 Production Data
SERIAL INTERFACE

t

t

WL

WH

SCLK

DIN

DOUT

X1 2

t

SUD

t

HD

XD15 D14 D13

X D15 * D14 * D13 * D12 * D1 * D0 * X

t

WHFStSUFSCLK

* DIN data from previous word

FS

(

µ

C MODE)

t

WLFS

FS

(DSP MODE)

Figure 1 Timing Diagram

SYMBOL TEST

CONDITIONS

t

SUFSCLK

t

C16-FS

Setup time, FS pin low before fi rst falling edge of SCLK
Setup time, 16th falling clock edge after FS l ow to ris i ng edge of FS

(only used in microcont rol l er mode)

t

WLOADB

t

WH

t

WL

t

SUD

t

HD

t

WHFS

t

WLFS

t

s

Pulse duration, LOADB low
Pulse duration, SCLK high
Pulse duration, SCLK low
Setup time, data ready before SCLK falling edge
Hold time, data held valid after SCLK falling edge
Pulse duration, FS high
Pulse duration, FS low
DAC Output settling ti me

34 16

(delayed by 16 clock cycles)

No high to low transitions

X

2

D1 D0 X

t

SUC16-FS

MIN TYP MAX UNIT

8ns

10 ns

10 ns
16 ns
16 ns

8ns

5ns
10 ns
10 ns

see Dynamic DAC Speci fications

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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Production Data WM2629

Figure

TYPICAL PERFORMANCE GRAPHS

0.3

0.2

0.1

0

-0.1

Integral Non-Linearity (LSBs)

-0.2

-0.3
0 32 64 96 128 160 192 224 256

DIGITAL CODE

Figure 2 Integral Non-Linearity

1

VDD = 3V

= 1.024V

V

REF

Input Code = 0

0.8

0.6

0.4

Output Voltage (V)

0.2

0

00.511.52

Sink Current (mA)

Slow
Fast

1

VDD = 5V
V

= 2.048V

REF

Input Code = 0

0.8

0.6

0.4

Output Voltage (V)

0.2

0

0 0.2 0.4 0.6 0.8 1 1 .2 1.4 1.6 1.8 2

Sink Current (mA)

Slow
Fast

Figure 3 Output Load Regulation (Sink) AVDD = 3V Figure 4 Output Load Regulation (Sink) AVDD = 5V

2.1

VDD=3V

=1.024V

V

REF

Input Code = 4095

2.08

2.06

2.04

DACA (Volts)

2.02

2

Sourcing Current (mA)

Slow
Fast

-4-3.5-3-2.5-2-1.5-1-0.50

4.15

VDD=5V

=2.048V

V

REF

Input Code = 4095

4.13

4.11

4.09

DACA (Volts)

4.07

4.05

Sourcing Curre nt (mA)

Slow
Fast

-4-3.5-3-2.5-2-1.5-1-0.50

Figure 5 Output Load Regulation (Source) AVDD = 3V

6 Output Load Regulation (Source) AVDD = 5V

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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WM2629 Production Data
DEVICE DESCRIPTION

GENERAL FUNCTION

The WM2629 is an octal 8-bi t, voltage output DAC. It contains a serial interface, control logic for
speed and power down, a programmable voltage reference, and eight digit al to analogue converters .
Each converter uses a resistor string network buffered with an op amp to convert 8-bit digital dat a to
analogue voltage levels (see Block Diagram). The output voltage is determined by the reference
input voltage and the input code according to the following relationship:

CODE

2

Output voltage =

INPUT OUTPUT

1111 1111

::

1000 0001

1000 0000

0111 1111

::

0000 0001

0000 0000 0V

Table 1 Binary Code Table

V

()

REF

256

2

()

REFV

2

()

REFV

()

2

2

()

REFV

2

()

REFV

128
256

255
256

129
256

REFREF VV =

127
256

1

256

POWER ON RESET

An internal power-on-reset circuit resets the DAC register to al l 0s on power-up.

BUFFER AMPLIFIER

The output buffer has a near rail-to-rail out put with short circuit protec tion and can reliably drive a
2kΩ load with a 100pF load capacitance.

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Production Data WM2629

SERIAL INTERFACE

INTERFACE MODES

The control interface can operate in two different modes:

• In the microcontroller mode, FS needs to be held low until all 16 data bits have been
transferred. If FS is dri ven high before the 16
The DAC is updated after a rising edge on FS .

• In DSP mode, FS only needs to stay low for 20ns, and can go high before the 16
edge.

SCLK

FS

X

D15

DIN

Figure 7 Interface Timing in Microcontroller Mode

SCLK

FS

DIN

X

D14 D1 D0 X E15

D15

D14 D1 D0 E15 E14 E0 X X F15

E14

th

falling clock edge, t he data transf er is cancell ed.

E1 E0 X F15

E1

X

X

th

falling clock

F14

F14

Figure 8 Interface Timing in DSP Mode

The operating mode is selected using pin 17 (MODE).

MODE PIN (17) INTERFACE MODE

HIGH Microcontroller

LOW or unconnected DSP mode

Table 2 Interface Mode Selection

SERIAL CLOCK AND UPDATE RATE

Figure 1 shows the interface timing. The maximum serial clock rate is:

f

Since a data word contains 16 bits, the sample rate is li mited to

f

However, the DAC settling tim e to 8 bi ts acc urac y lim it s t he respons e ti m e of t he analogue output f or
large input step transitions.

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

SCLK

s

max

max

=

=

16

1

tt

+

WLWH

1

tt

+

()

WLWH

MHz

31

=

minmin

MHz

95.1

=

minmin

9

WM2629 Production Data

DAISY CHAINING MULTIPLE DEVICES

The DOUT output (pin 19) provides the data sam pled on DIN with a delay of 16 c lock cycles. This
signal can be used to control anot her WM2629 or similar devi ce in a daisy-chain type circuit.

DIN

SCLK

LOADB

FS

FS

DIN

SCLK

DOUT

LOADB

OCTAL DAC #1

Figure 9 Daisy Chaining

SOFTWARE CONFIGURATION OPTIONS

DATA FORMAT

The WM2629 is controll ed with a 16-bit code consisting of four address bi ts, A0-A3, and up to 12
data bits.

D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

A3 A2 A1 A0 Data

Table 3 Input Data Format

Using the four address bits , 16 different registers c an be addressed.

A3 A2 A1 A0 REGISTER

0 0 0 0 DAC A Code
0 0 0 1 DAC B Code
0 0 1 0 DAC C Code
0 0 1 1 DAC D Code
0 1 0 0 DAC E Code
0 1 0 1 DAC F Code
0 1 1 0 DAC G Code
0 1 1 1 DAC H Code
1 0 0 0 Control Register 0
1 0 0 1 Control Register 1
1 0 1 0 Preset all DACs
1 0 1 1 RESERVED
1 1 0 0 DA C A and complement B
1 1 0 1 DAC C and compl ement D
1 1 1 0 DAC E and complem ent F
1 1 1 1 DAC G and complement H

Table 4 Register Map

FS

DIN

SCLK

LOADB

OCTAL DAC #2

FS

DIN

DOUT

OCTAL DAC #3

SCLK

DOUT

LOADB

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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Production Data WM2629

DAC A TO H CODE REGISTERS

Addresses 0 to 7 are the DAC registers. Bits D11 (MSB) to D4 (LSB) from these registers are
transferred to the respect ive DAC when the LOADB input (pin 18) is low. Bit s D3 to D1 are unused
and must be set to 0. For i nstantaneous updating, LOADB can be hel d l ow perm anently.

CONTROL REGISTER 0

Control register 0 (address 8) is used to select func tions that apply to the whole IC, such as Power
Down and Data Input Format.

BIT D11 D10D9D8D7D6D5 D4 D3 D2 D1 D0

Function X X XXXXXPDDO X X IM

Default X X XXXXX 0 0000

Table 5 Control Register 0 Map

BIT DESCRIPTION 0 1

PD Full device Power Down Normal Power D own
DO DOUT Enable Disabled Enabled

IM Input Mode Straight Binary Two’s Complement

X Reserved

Table 6 Control Register 0 Functionality

CONTROL REGISTER 1

Control register 1 (address 9) is used to power down individual pairs of DACs and s elect thei r set tl ing
time. Powering down a pair of DACs disabl es their am plif iers and reduces the power cons umpt ion of
the device. The settling t ime in fas t mode is typically 1µs. In s low mode, the s ettling time is typic ally
3µs and power consumption is reduced.

BIT D11 D10D9D8D7D6D5 D4 D3 D2 D1 D0

Function X X X X PGHPEFPCDP

S

S

S

AB

GH

EF

S

CD

AB

Default X X X X 0 0 0 0 0 0 0 0

Table 7 Control Register 1 Map

BIT DESCRIPTION 0 1

P

XY

S

XY

Power Down DACs X and Y Normal Power Down

Speed Setting for DACs X and Y Slow Fast

Table 8 Control Register 1 Functionality

DAC PRESET REGISTER

The Preset register (address 10) m akes it possi ble to update all eight DACs at the same t ime. The
value stored in this register becomes the digital input to all the DACs when the asynchronous PRE B
input (pin 5) is driven low. If no data has previously been written to the preset register, all DA Cs are
set to zero scale.

TWO-CHANNEL REGISTERS

The two-channel registers (addresses 12 t o 15) provide a ‘differential output’ func tion where writing
data to one DAC will automatically write the complem ent to the other DAC in the pair. For example,
writing a value of 255 to address 12 will set DAC A to full scale and DAC B to zero scale.

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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WM2629 Production Data
APPLICATIONS INFORMATION

LINEARITY, OFFSET, AND GAIN ERROR

Amplifiers operating from a single supply can have positive or negative voltage offsets. With a
positive offset, the output voltage changes on the first code transition. However, if the offset is
negative, the output voltage m ay not change with the first code, depending on t he magnitude of the
offset voltage. This i s because with the m ost negat ive supply rail being ground, any att empt to drive
the output amplifier below ground will clamp the output at 0 V. The output voltage t hen remains at
zero until the input code is s ufficiently high to overc ome the negative offs et voltage, resulting in the
transfer function shown in Figure 10.

Output

Voltage

0 V

Negative

Offset

Figure 10 Effect of Negative Offset

This offset error, not t he linearity error, produces the break point. The transfer function would follow
the dotted line if the output buf fer could drive below the ground rail.

DAC linearity is measured between zero-input code (all input bi ts at 0) and full -scale code (al l inputs
at 1), disregarding offset and full-scale errors. However, due to the break poi nt in the transfer function,
single supply operation does not al low for adjustm ent when the offs et is negative. In s uch cas es, the
linearity is therefore m easured between full-s cale and the l owest code that produces a posi tive (non­zero) output voltage.

DAC code

POWER SUPPLY DECOUPLING AND GROUNDING

Printed circuit boards with separate analogue and digital ground planes deliver the best system
performance. The two ground planes should be connected together at the low impedance power
supply source. Ground currents should be managed so as to minimise voltage drops across the
ground planes.

A 0.1µF decoupling capacitor should be connected between the pos itive supply and ground pins of
the DAC, with short leads as close as possibl e to the devic e. Use of f errite beads may f urther isolat e
the system analogue suppl y from the digital supply.

WOLFSON MICROELECTRONICS LTD PD Rev 1.0 April 2001

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Production Data WM2629

PACKAGE DIMENSIONS

DT: 20 PIN TSSOP (6.5 x 4.4 x 1.0 mm)

b

A1

A2

A

e

1120

D

101

0.1

E1 E

C

-C-

SEATING PLANE

GAUGE
PLANE

DM008.D

θ

0.25

c

L

Dimensions

Symbols

(mm)

MIN NOM MAX
A
A

1

A

2

b
c
D
e
E
E

1

L

θ

REF:

NOTES:
A. ALL LINEAR DIMENSIONS ARE IN MILLIMETERS.
B. THIS DRAWING IS SUBJECT TO CHANGE WITHOUT NOTICE.
C. BODY DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSION, NOT TO EXCEED 0.25MM.
D. MEETS JEDEC.95 MO-153, VARIATION = AC. REFER TO THIS SPECIFICATION FOR FURTHER DETAILS.

----- ----- 1.20

0.05 ----- 0.15

0.80 1.00 1.05

0.19 ----- 0.30

0.09 ----- 0.20

6.40 6.50 6.60

0.65 BSC

6.4 BSC

4.30 4.40 4.50

0.45 0.60 0.75

o

0

----- 8

JEDEC.95, MO-153

o

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