completing a conversion. The reference and reference

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.

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

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

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