WM2604
Production Data
SERIAL INTERFACE
Explanation of data transfer:
First, the device has to be enabled with NCS set to low. Then, a falling edge of FS starts shifting the data
bit-per-bit (starting with the MSB) to the internal register on the falling edges of SCLK. After 16 bits have
been transferred, the next rising edge on SCLK or FS causes the content of the shift register to be moved
to the DAC holding latch. If NLDAC is low, the DAC latch will also be updated immediately.
The serial interface of the device can be used in two basic modes:
•
•
four wire (with chip select)
three wire (without chip select)
Using chip select (four wire mode), it is possible to have more than one device connected to the serial port
of the data source (DSP or microcontroller). If there is no need to have more than one device on the serial
bus, then NCS can be tied low.
SERIAL CLOCK AND UPDATE RATE
Figure 1 shows the device timing. The maximum serial rate is:
f
SCLK
max =
1
=
20MHz
t
WCH min
+
t
WCL min
The digital update rate is limited to an 800ns period, or 1.25MHz frequency. However, the DAC settling
time to 10 bits limits the update rate for large input step transitions.
SOFTWARE CONFIGURATION OPTIONS
The 16 bits of data can be transferred with the sequence shown in Table 2. D11-D2 contains the
10-bit data word. D15-D12 hold the programmable options.
D15
A1
D14
A0
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
X
D0
X
PWR SPD
New DAC value (10 bits)
Table 2 Register Map
DAC ADDRESSING
A particular DAC (A, B, C, D) within the device is selected by A1 and A0 within the input word.
A1
0
0
1
1
A0
0
1
0
1
DAC ADDRESS
DAC A
DAC B
DAC C
DAC D
PROGRAMMABLE SETTLING TIME (SPD – BIT D12)
Settling time is a software selectable 12µs or 4µs, typical to within
±0.5LSB
of final value. This is
controlled by the value of SPD – Bit D12 and an associated DAC address. A ONE defines a settling time
of 4µs, a ZERO defines a settling time of 12µs for that DAC.
PROGRAMMABLE POWER DOWN
The power down function is controlled by PWR - Bit D13 and an associated DAC address. A ZERO
configures that DAC as active, a ONE configures that DAC into power down mode.
WOLFSON MICROELECTRONICS LTD
PD Rev 1.0 June 99
9
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
