TLC3544_07 Datasheet, PDF (34/42 Pages) Texas Instruments – 5-V ANALOG, 3-/5-V DIGITAL, 14-BIT, 200-KSPS, 4-/8-CHANNELS SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH 0-5 V (PSEUDODIFFERENTIAL) INPUTS

TLC3544, TLC3548
5-V ANALOG, 3-/5-V DIGITAL, 14-BIT, 200-KSPS, 4-/8-CHANNELS SERIAL
ANALOG-TO-DIGITAL CONVERTERS WITH 0-5 V (PSEUDODIFFERENTIAL) INPUTS
SLAS266C – OCTOBER 2000 – REVISED MAY 2003
APPLICATION INFORMATION
interface with host
Figure 34 shows examples of the interface between a single converter and a host DSP (TMS320C54x DSP)
or microprocessor. The C54x is set as FWID = 1 (active pulse width = 1CLK), (R/X) DATDLY = 1 (1 bit data delay),
CLK(X/R)P = 0 (transmit data are clocked out at rising edge of CLK, receive data are sampled on falling edge
of CLK), and FS(X/R)P = 1 (FS is active high). If multiple converters connect to the same C54x, use CS as the
chip select.
The host microprocessor is set as the SPI master with CPOL = 0 (active high clock), and CPHA = 1 (transmit
data is clock out at rising edge of CLK, receive data are sampled at falling edge of CLK). 16 bits (or more) per
transfer is required.
VDD
VDD
TMS320C54X
FSR
FSX
DX
DR
CLKR
CLKX
IRQ
10 kΩ
10 kΩ
10 kΩ
Converter
CS
FS
SDI
SDO
Host
Microprocessor
SS
Ain
MOSI
MISO
Converter
CS
FS
Ain
SDI
SDO
SCLK
INT/EOC
SCK
IRQ
SCLK
INT/EOC
Single Converter Connects to DSP
Converter Connects to Microprocessor
Figure 34. Typical Interface to Host DSP and Microprocessor
sampling time analysis
Figure 35 shows the equivalent analog input circuit of the converter. During the sampling, the input capacitor,
C_i, has to be charged to V_C, (V_C = V_s ± voltage of 1/4 LSB = V_s ± [V_s/65532] for 14 bit converter).
t_(s) = R_t × C_i × In (65532) where R_t = R_s+r_i, t_(s) = Sampling time
Driving Source
Data Converter
VS
RS
VI
ri
VC
CI
VI = Input Voltage at AIN
VS = External Driving Source Voltage
RS = Source Resistance
ri = Equivalent Resistor of Mux., 1.5 kΩ
CI = Input Capacitance, 30 pF Max.
VC = Capacitance Charging Voltage
Figure 35. Equivalent Input Circuit Including the Driving Source
TMS320C54x is a trademark of Texas Instruments.
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