Datasheet

LTC2389-16
33
238916f
applications inFormation
Serial Bus Configuration
In applications where a serial bus is required to minimize
the data bus width, the LTC2389-16 is capable of provid-
ing each conversion result R[15:0] serially on pin D10/
SDO. To select this bus configuration, pin MODE0 should
be driven to MODE0 = 1, as described in Table 1. Address
input pin A1 has no effect on the parsing or presentation
of serial conversion data. As shown in Figure 18, the serial
output data is presented on the SDO pin in response to an
external shift clock input applied to the SCK pin. The data
on SDO changes state following rising edges of SCK. The
one exception to this behavior is that D15 remains valid
until the first SCK rising edge following the first SCK falling
edge. If CS is used to gate the serial output data, the full
conversion result should be read before CS is returned to
a high level. For best performance, do not clock serial data
out when BUSY is high. The SDI input pin can be used to
daisy chain multiple converters, as shown in Figure 18.
In this figure, two devices are cascaded with the MSB of
ADC1 appearing at the serial output of
ADC2 after a 16
SCK
cycle delay. The serial output of ADC1 is clocked
into ADC2 on the falling edges of SCK. This is useful in
applications where hardware constraints limit the number
of data lines available to interface with multiple converters.
Data Format
The binary format of the conversion result depends on the
state of pins PD/FD and OB/2C, as described in Table2.
These pins are active in both the parallel and serial modes
of operation.
Reset
As shown in Figure 19, when the RESET pin is high, the
LTC2389-16 is reset and the data bus is put into a high
impedance mode. If this occurs during a conversion, the
conversion is immediately halted. In reset, requests for
new conversions are ignored. Once RESET returns low,
the LTC2389-16 is ready to start a new conversion after
the acquisition time has been met.
Figure 19. RESET Pin Timing
RESET
DATA BUS D[15:0]
Hi-Z
CVNST
t
RESETH
t
ACQ
238916 F19