WM2627
Production Data
SERIAL INTERFACE
To start transferring data, the device first 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:
1
fSCLKmax =
= 20MHz
tWCH min+ tWCL min
The digital update rate is limited to an 800ns period, or 1.25MHz frequency. However, the DAC
settling time to 8 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
8-bit data word. D15-D12 hold the programmable options.
D15 D14 D13 D12 D11 D10 D9
D8
D7
D6
D5
D4
D3
0
D2
0
D1
0
D0
0
A1 A0 PWR SPD New DAC value (8 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
A0
0
DAC ADDRESS
DAC A
0
1
DAC B
1
0
DAC C
1
1
DAC D
PROGRAMMABLE SETTLING TIME (SPD – BIT D12)
Settling time is a software selectable 2.5µs or 8.5µs, typical to within ±0.1LSB 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 2.5µs, a ZERO defines a settling time of 8.5µs 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 April 2001
9
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
