MAX146 Maxim, MAX146 Datasheet - Page 21

• Manufacturer Part Number: MAX146
• Description: +2.7Low-Power / 8-Channel / Serial 12-Bit ADCs
• Manufacturer: Maxim

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
2) The MAX146/MAX147’s CS pin is driven low by the
3) An 8-bit word (1XXXXX11) should be written to the
Figure 18. Bipolar Transfer Function, Full Scale (FS) =
VREF / 2 + COM, Zero Scale (ZS) = COM
*COM
011 . . . 111
011 . . . 110
000 . . . 010
000 . . . 001
000 . . . 000
111 . . . 111
111 . . . 110
111 . . . 101
100 . . . 001
100 . . . 000
(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.
TMS320’s XF_ I/O port to enable data to be clocked
into the MAX146/MAX147’s DIN.
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.
VREF / 2
OUTPUT CODE
-FS =
1LSB =
- FS
FS = VREF
ZS = COM
-VREF
2
2
______________________________________________________________________________________
VREF
4096
+ COM
+ COM
INPUT VOLTAGE (LSB)
TMS320LC3x Interface
COM*
+FS - 1LSB
+2.7V, Low-Power, 8-Channel,
4) The MAX146/MAX147’s SSTRB output is monitored
5) The TMS320 reads in one data bit on each of the
6) Pull CS high to disable the MAX146/MAX147 until
Figure 19. Power-Supply Grounding Connection
R* = 10
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.
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.
the next conversion is initiated.
*OPTIONAL
V
+3V
DD
Serial 12-Bit ADCs
AGND
MAX146
MAX147
SUPPLIES
COM
DGND
+3V
+3V
CIRCUITRY
DIGITAL
DGND
GND
21