MAX146ACAP Просмотр технического описания (PDF) - Maxim Integrated

Номер в каталоге

Компоненты Описание

производитель

MAX146ACAP

+2.7V, Low-Power, 8-Channel, Serial 12-Bit ADCs

Maxim Integrated 

+2.7V, Low-Power, 8-Channel,

Serial 12-Bit ADCs

COMPLETE CONVERSION SEQUENCE

DIN 1

00

FULLPD

REFADJ

1.21V

0V

(ZEROS)

9ms WAIT

1

01

FASTPD

CH1

1

11

NOPD

2.50V

VREF

0V

τ = RC = 20kΩ x CREFADJ

tBUFFEN ≈ 200µs

Figure 15. MAX146 FULLPD/FASTPD Power-Up Sequence

CH7

1

00

FULLPD

(ZEROS)

1

01

FASTPD

Lowest Power at Higher Throughputs

Figure 14b shows the power consumption with

external-reference compensation in fast power-down,

with one and eight channels converted. The external

4.7µF compensation requires a 200µs wait after

power-up with one dummy conversion. This graph

shows fast multi-channel conversion with the lowest

power consumption possible. Full power-down mode

may provide increased power savings in applications

where the MAX146/MAX147 are inactive for long peri-

ods of time, but where intermittent bursts of high-speed

conversions are required.

Internal and External References

The MAX146 can be used with an internal or external

reference voltage, whereas an external reference is

required for the MAX147. An external reference can be

connected directly at VREF or at the REFADJ pin.

An internal buffer is designed to provide 2.5V at

VREF for both the MAX146 and the MAX147. The

MAX146’s internally trimmed 1.21V reference is buf-

fered with a 2.06 gain. The MAX147’s REFADJ pin is

also buffered with a 2.00 gain to scale an external 1.25V

reference at REFADJ to 2.5V at VREF.

Internal Reference (MAX146)

The MAX146’s full-scale range with the internal refer-

ence is 2.5V with unipolar inputs and ±1.25V with bipo-

lar inputs. The internal reference voltage is adjustable

to ±1.5% with the circuit in Figure 16.

External Reference

With both the MAX146 and MAX147, an external refer-

ence can be placed at either the input (REFADJ) or the

output (VREF) of the internal reference-buffer amplifier.

The REFADJ input impedance is typically 20kΩ for the

MAX146, and higher than 100kΩ for the MAX147. At

+3.3V

24k

100k

510k

0.047µF

MAX146

12 REFADJ

Figure 16. MAX146 Reference-Adjust Circuit

Table 5. Software Power-Down and

Clock Mode

PD1

PD0

0

0

0

1

1

0

1

1

DEVICE MODE

Full Power-Down

Fast Power-Down

Internal Clock

External Clock

Table 6. Hard-Wired Power-Down and

Internal Clock Frequency

SHDN

STATE

1

Floating

0

DEVICE

MODE

Enabled

Enabled

Power-Down

REFERENCE

BUFFER

COMPENSATION

Internal

External

N/A

INTERNAL

CLOCK

FREQUENCY

225kHz

1.8MHz

N/A

______________________________________________________________________________________ 19

Share Link: