MAX127ACAI(2012) Просмотр технического описания (PDF) - Maxim Integrated

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производитель

MAX127ACAI
(Rev.:2012)

Multirange, +5V, 12-Bit DAS with 2-Wire Serial Interface

Maxim Integrated 

MAX127/MAX128

Multirange, +5V, 12-Bit DAS with

2-Wire Serial Interface

REF

MAX127

MAX128

AV = 1.638

REFADJ

10kΩ

2.5V

CREF

4.7µF

0.01µF

Figure 11a. Internal Reference

MAX127

MAX128

REF

AV = 1.638

REFADJ

10kΩ

2.5V

4.096V

CREF

4.7µF

VDD

Figure 11b. External Reference, Reference at REF

MAX127

MAX128

REF

AV = 1.638

REFADJ

10kΩ

2.5V

CREF

4.7µF

2.5V

0.01µF

Figure 11c. External Reference, Reference at REFADJ

www.maximintegrated.com

+5V

100kΩ

24kΩ

510kΩ

0.01µF

REFADJ

MAX127

MAX128

Figure 12. Reference-Adjust Circuit

To power-up from a software-initiated power-down, a

START condition followed by the correct slave address

must be received (with R/W = 0). The MAX127/MAX128

power-up after receiving the next bit.

For hardware-controlled power-down (FULLPD), pull

SHDN low. When hardware shutdown is asserted, it

becomes effective immediately and any conversion in

progress is aborted.

Choosing Power-Down Modes

The bandgap reference and reference buffer remain

active in STBYPD mode, maintaining the voltage on the

4.7μF capacitor at REF. This is a “DC” state that does not

degrade after standby power-down of any duration.

In FULLPD mode, only the bandgap reference is active.

Connect a 33μF capacitor between REF and AGND to

maintain the reference voltage between conversions and

to reduce transients when the buffer is enabled and dis-

abled. Throughput rates down to 1ksps can be achieved

without allotting extra acquisition time for reference recov-

ery prior to conversion. This allows conversion to begin

immediately after power-down ends. If the discharge of

the REF capacitor during FULLPD exceeds the desired

limits for accuracy (less than a fraction of an LSB), run a

STBYPD power-down cycle prior to starting conversions.

Take into account that the reference buffer recharges the

bypass capacitor at an 80mV/ms slew rate, and add 50μs

for settling time.

Auto-Shutdown

Selecting STBYPD on every conversion automatically

shuts the MAX127/MAX128 down after each conversion

without requiring any start-up time on the next conversion.

Maxim Integrated │  14

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