WM2614 Просмотр технического описания (PDF) - Wolfson Microelectronics plc

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WM2614

Quad 12-bit Serial Input Voltage Output DAC

Wolfson Microelectronics plc 

Production Data Rev 1.0

WM2614

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 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:

fSCLKmax =

1

tWCH min + tWCL min

= 20MHz

The digital update rate is limited to an 800ns period, or 1.25MHz frequency. However, the DAC settling

time to 12 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-D0 contains the 12-bit

data word. D15-D12 hold the programmable options.

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

A1 A0 PWR SPD

New DAC value (12 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

A0

0

0

0

1

1

0

1

1

DAC ADDRESS

DAC A

DAC B

DAC C

DAC D

PROGRAMMABLE SETTLING TIME

Settling time is a software selectable 12µs or 4µs, typical to within ±0.5LSB of final value. This is

controlled by the value of D12 and 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 D13. A ZERO configures that DAC as active, a ONE configures

that DAC into power down mode. When the power down function is released the device reverts to the

DAC code set prior to power down.

WOLFSON MICROELECTRONICS LTD

Production Data Rev 1.0 June 1999

9

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