16

LTC1419

DIGITAL INTERFACE

The A/D converter is designed to interface with micropro-

cessors as a memory mapped device. The CS and RD

control inputs are common to all peripheral memory

interfacing. A separate CONVST is used to initiate a

conversion.

Internal Clock

The A/D converter has an internal clock that eliminates the

need of synchronization between the external clock and

the CS and RD signals found in other ADCs. The internal

clock is factory trimmed to achieve a typical conversion

time of 0.95

µs and a maximum conversion time over the

full operating temperature range of 1.15

µs. No external

adjustments are required. The guaranteed maximum

acquisition time is 300ns. In addition, a throughput time of

1.25

µs and a minimum sampling rate of 800ksps are

guaranteed.

Power Shutdown

The LTC1419 provides two power shutdown modes, nap

and sleep, to save power during inactive periods. The nap

CS

SHDN

1419 F14a

Figure 14a. CS to SHDN Timing

mode reduces the power by 95% and leaves only the

digital logic and reference powered up. The wake-up time

from nap to active is 200ns. In sleep mode the reference

is shut down and only a small current remains, about

250

µA. Wake-up time from sleep mode is much slower

since the reference circuit must power up and settle to

0.005% for full 14-bit accuracy. Sleep mode wake-up

time is dependent on the value of the capacitor connected

to the REFCOMP (Pin 4). The wake-up time is 10ms with

the recommended 10

µF capacitor. Shutdown is con-

trolled by Pin 21 (SHDN); the ADC is in shutdown when it

is low. The shutdown mode is selected with Pin 20 (CS);

low selects nap.

Figure 13d. Suggested Evaluation Circuit Board—Solder Side Layout