Rainbow Electronics MAX1189 - Manual (Page 9)

completing a conversion. The reference and reference
buffer require a minimum of 12ms (C
REFADJ
= 0.1µF,
C REF = 10µF) to power up and settle from shutdown.
The state of R/C during the second falling edge of CS
selects which power-down mode the MAX1179/
MAX1187/MAX1189 enters upon conversion comple-
tion. Holding R/C low causes the MAX1179/MAX1187/
MAX1189 to enter standby mode. The reference and
buffer are left on after the conversion completes. R/C
high causes the MAX1179/MAX1187/MAX1189 to enter
shutdown mode and power down the reference and
buffer after conversion (see Figures 5 and 6). Set the
voltage at REF high during the second falling edge of
CS to realize the lowest current operation.
Standby Mode
While in standby mode, the supply current is less than
3.7mA (typ). The next falling edge of CS with R/C low
causes the MAX1179/MAX1187/MAX1189 to exit stand-
by mode and begin acquisition. The reference and ref-
erence buffer remain active to allow quick turn-on time.
MAX1179/MAX1187/MAX1189
16-Bit, 135ksps, Single-Supply ADCs with
Bipolar Analog Input Range
_______________________________________________________________________________________ 9
Figure 4. Equivalent Input Circuit
MAX1187
R2
R3
161 Ω
3.4k Ω
TRACK
TRACK
HOLD
HOLD
S1, S2 = T/H SWITCH
S3 = POWER-DOWN
(MAX1179/MAX1189
ONLY)
S1
C HOLD
30pF
S2
AIN
MAX1179/MAX1189
R2
R3
161 Ω
3.4k Ω
S3
POWER-
DOWN
TRACK
TRACK
HOLD
HOLD
REF
R2 = 7.85k Ω (MAX1189)
OR 3.92k Ω (MAX1179/MAX1187)
R3 = 5.45k Ω (MAX1189)
OR 17.79k Ω (MAX1179/MAX1187)
S1
C HOLD
30pF
S2
AIN
T/H OUT T/H OUT
Figure 5. Selecting Standby Mode
CS
R/C
EOC
ACQUISITION CONVERSION
DATA
OUT
REF AND
BUFFER
POWER