Rainbow-electronics MAX159 Manual de usuario descargar pdf (Pagina 12)

MAX157/MAX159

QSPI Interface

Using the high-speed QSPI interface with CPOL = 0

and CPHA = 0, the MAX157/MAX159 supports a maxi-

mum f

SCLK

of 2.17MHz. The QSPI circuit in Figure 9a

can be programmed to perform a conversion on each

of the two channels for the MAX157.

Figure 9b shows the QSPI interface timing.

PIC16 with SSP Module

and PIC17 Interface

The MAX157/MAX159 are compatible with a PIC16/

PIC17 microcontroller (µC), using the synchronous seri-

al port (SSP) module.

To establish SPI communication, connect the controller

as shown in Figure 10a and configure the PIC16/PIC17

as system master by initializing its synchronous serial

port control register (SSPCON) and synchronous serial

port status register (SSPSTAT) to the bit patterns shown

in Tables 2 and 3.

In SPI mode, the PIC16/PIC17 µCs allow eight bits of

data to be synchronously transmitted and received

simultaneously. Two consecutive 8-bit readings (Figure

10b) are necessary to obtain the entire 10-bit result

from the ADC. DOUT data transitions on the serial

clock’s falling edge and is clocked into the µC on

SCLK’s rising edge. The first 8-bit data stream contains

three leading ones, the channel identification, and the

first four data bits starting with the MSB. The second 8-

bit data stream contains the remaining bits, D5 through

D0, and the two sub-bits S1 and S0.

Layout, Grounding, and Bypassing

For best performance use printed circuit boards

(PCBs), wire-wrap configurations are not recommend-

ed, since the layout should ensure proper separation of

analog and digital traces. Run analog and digital lines

anti-parallel to each other, and don’t layout digital sig-

nal paths underneath the ADC package. Use separate

analog and digital PCB ground sections with only one

+2.7V, Low-Power, 2-Channel,

108ksps, Serial 10-Bit ADCs in 8-Pin µMAX

12 ______________________________________________________________________________________

HIGH-Z

SAMPLING

INSTANT

D9CHID D8 D7 D6 D5

12345678 109111213141516

D4 D3 D2 D1 D0 S0S1

DOUT*

CS/SHDN

SCLK

1ST BYTE READ 2ND BYTE READ

MSB

LSB

*WHEN CS/SHDN IS HIGH, DOUT = HIGH -Z

Figure 8c. SPI/MICROWIRE Interface Timing Sequence (CPOL = CPHA = 0)

CS/SHDN

SCLK

DOUT

SCK

MISO

QSPI

MAX157

MAX159

Figure 9a. QSPI Connections

MAX157

MAX159

CS/SHDN

SCLK

DOUT

I/O

MICROWIRE

CS/SHDN

SCLK

DOUT

I/O

SCK

MISO

SPI

MAX157

MAX159

Figure 8a. SPI Connections Figure 8b. MICROWIRE Connections

1 2 ... 7 8 9 10 11 12 13 14 15 16

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