Starting SCLK before conversion is complete corrupts

the conversion in progress, and the data clocked out at

DOUT does not represent the input signal. Bringing

CONVST high at anytime during a conversion or while

the data is clocked out will result in an incorrect conver-

sion. A new conversion can be restarted only if all eight

data bits of conversion have been clocked out. Toggle

CONVST after all data is clocked out to restart a new

conversion.

SHDN is used to place the MAX1106/MAX1107 in low-

power mode (see

Power-Down section). In this mode

DOUT is high impedance and any conversion in

progress is stopped immediately. If a conversion is

stopped by SHDN going low, the device must be reset

by waiting 35µs and clearing the output register with

eight SCLKs before the next conversion.

How to Perform a Conversion

The MAX1106/MAX1107 converts an input signal using

the internal clock. This frees the µP from the burden of

running the SAR conversion clock, and allows the con-

version results to be read back at the µP’s convenience

at any clock rate up to 2MHz.

Figures 6 and 7 show the serial interface timing charac-

teristics. CONVST idles low. Toggle CONVST high for at

least 1µs to perform the autozero adjustment. After

CONVST goes low, conversion starts immediately.

Allow 35µs for the internal conversion to complete and

issue the MSB of the conversion at DOUT. CONVST

needs to be held low once a conversion is started,

while SCLK should remain low during conversion for

best noise performance. An internal register stores data

when the conversion is in progress. SCLK clocks the

CONVST

SCLK

1

µs

(MIN)

HIGH-Z

HIGH-Z

DOUT

18

100

µs (MAX)

D7

MSB

LSB

D6

D5

D4

D3

D2

D1

D0

CONVERSION

ACQUISITION

A/D STATE

ACQ

Figure 6. Conversion Timing Diagram

Single-Supply, Low-Power,

Serial 8-Bit ADCs

12

______________________________________________________________________________________

CONVST

SCLK

DOUT

I/O

SCK

MISO

+3V

SS

a) SPI

CONVST

CONVST

SCLK

DOUT

CS

SCK

MISO

+3V

SS

b) QSPI

MAX1106

MAX1107

MAX1106

MAX1107

MAX1106

MAX1107

SCLK

DOUT

I/O

SK

SI

c) MICROWIRE

Figure 5. Common Serial-Interface Connections