MAX147ACAP Просмотр технического описания (PDF) - Maxim Integrated

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MAX147ACAP

+2.7V, Low-Power, 8-Channel, Serial 12-Bit ADCs

Maxim Integrated 

+2.7V, Low-Power, 8-Channel,

Serial 12-Bit ADCs

OUTPUT CODE

011 . . . 111

011 . . . 110

000 . . . 010

000 . . . 001

000 . . . 000

111 . . . 111

111 . . . 110

111 . . . 101

FS = VREF + COM

2

ZS = COM

-FS = -VREF + COM

2

1LSB = VREF

4096

100 . . . 001

100 . . . 000

- FS

*COM VREF / 2

COM*

INPUT VOLTAGE (LSB)

+FS - 1LSB

+3V

R* = 10Ω

SUPPLIES

+3V GND

VDD

AGND

COM DGND

*OPTIONAL

MAX146

MAX147

+3V DGND

DIGITAL

CIRCUITRY

Figure 18. Bipolar Transfer Function, Full Scale (FS) =

VREF / 2 + COM, Zero Scale (ZS) = COM

TMS320LC3x Interface

Figure 21 shows an application circuit to interface the

MAX146/MAX147 to the TMS320 in external clock mode.

The timing diagram for this interface circuit is shown in

Figure 22.

Use the following steps to initiate a conversion in the

MAX146/MAX147 and to read the results:

1) The TMS320 should be configured with CLKX

(transmit clock) as an active-high output clock and

CLKR (TMS320 receive clock) as an active-high

input clock. CLKX and CLKR on the TMS320 are

tied together with the MAX146/MAX147’s SCLK

input.

2) The MAX146/MAX147’s CS pin is driven low by the

TMS320’s XF_ I/O port to enable data to be clocked

into the MAX146/MAX147’s DIN.

3) An 8-bit word (1XXXXX11) should be written to the

MAX146/MAX147 to initiate a conversion and place

the device into external clock mode. Refer to Table

1 to select the proper XXXXX bit values for your

specific application.

Figure 19. Power-Supply Grounding Connection

4) The MAX146/MAX147’s SSTRB output is monitored

via the TMS320’s FSR input. A falling edge on the

SSTRB output indicates that the conversion is in

progress and data is ready to be received from the

MAX146/MAX147.

5) The TMS320 reads in one data bit on each of the

next 16 rising edges of SCLK. These data bits rep-

resent the 12-bit conversion result followed by four

trailing bits, which should be ignored.

6) Pull CS high to disable the MAX146/MAX147 until

the next conversion is initiated.

______________________________________________________________________________________ 21

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