Rainbow Electronics MAX149 - Manual (Page 15)

MAX148/MAX149
+2.7V to +5.25V, Low-Power, 8-Channel,
Serial 10-Bit ADCs
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delay and maximum sample rate. In external compensa-
tion mode, power-up time is 20ms with a 4.7µF compen-
sation capacitor when the capacitor is initially fully
discharged. From fast power-down, start-up time can be
eliminated by using low-leakage capacitors that do not discharge more than 1/2LSB while shut down. In power-
down, leakage currents at VREF cause droop on the ref-
erence bypass capacitor. Figures 12a and 12b show
the various power-down sequences in both external and
internal clock modes.
SCLK
DIN
DOUT
CS
S CONTROL BYTE 0 CONTROL BYTE 1 S
CONVERSION RESULT 0
B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 S1 S0
CONVERSION RESULT 1
SSTRB
B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 S1 S0
CONTROL BYTE 2 S
1 8 1 15 15 8 1
Figure 11a. External Clock Mode, 15 Clocks/Conversion Timing
CS
SCLK
DIN
DOUT
S
1 8 16 1 8 16
CONTROL BYTE 0 CONTROL BYTE 1 S
CONVERSION RESULT 0
B9 B8 B7 B6 B5 B4 B3 B2 B1 B0 S1 S0 B9 B8 B7 B6
CONVERSION RESULT 1
• • •
• • •
• • •
• • •
Figure 11b. External Clock Mode, 16 Clocks/Conversion Timing
POWERED UP
HARDWARE
POWER-
DOWN
POWERED UP
POWERED UP
10 + 2 DATA BITS 10 + 2 DATA BITS
INVALID
DATA
VALID
DATA
EXTERNAL EXTERNAL
S X X X X X 1 1 S 0 0 X X X X X X X X X X S 1 1
SOFTWARE
POWER-DOWN
MODE
DOUT
DIN
CLOCK
MODE
SHDN
SETS EXTERNAL
CLOCK MODE SETS EXTERNAL
CLOCK MODE
SETS SOFTWARE
POWER-DOWN
Figure 12a. Timing Diagram Power-Down Modes, External Clock