TLC2551_16 Datasheet, PDF (4/28 Pages) Texas Instruments – 5-V, LOW-POWER, 12-BIT, 175/360 KSPS, SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTOPOWER DOWN

TLC2551, TLC2552, TLC2555
5-V, LOW-POWER, 12-BIT, 175/360 KSPS,
SERIAL ANALOG-TO-DIGITAL CONVERTERS WITH AUTOPOWER DOWN
SLAS276D – MARCH 2000 – REVISED MAY 2003
detailed description (continued)
Charge
Redistribution
DAC
AIN
_
Control
+
Logic
ADC Code
GND/AIN(–)
Figure 1. Simplified SAR Circuit
serial interface
OUTPUT DATA FORMAT
MSB
LSB
D15–D4
D3–D0
Conversion result (OD11–OD0)
Don’t care
The output data format is binary (unipolar straight binary).
binary
Zero-scale code = 000h, Vcode = GND
Full-scale code = FFFh, Vcode = V_REF – 1 LSB
pseudo-differential inputs
The TLC2555 operates in pseudo-differential mode. The inverted input is available on pin 5. It can have a
maximum input ripple of ±0.2 V. This is normally used for ground noise rejection.
control and timing
start of the cycle
Each cycle may be started by either CS, FS, or a combination of both. The internal state machine requires one
SCLK high-to-low transition to determine the state of these control signals so internal blocks can be powered
up in an active cycle. Special care to SPI mode is necessary. Make sure there is at least one SCLK whenever
CS (pin 1) is high to assure proper operation.
TLC2551
D Control via CS ( FS = 1 at the falling edge of CS)—The falling edge of CS is the start of the cycle. The MSB
may be read on the first falling SCLK edge after CS is low. Output data changes on the rising edge of SCLK.
This is typically used for a microcontroller with an SPI interface, although it can also be used for a DSP. The
microcontroller SPI interface may be programmed for CPOL = 0 (serial clock referenced to ground) and
CPHA = 1 (data is valid on the falling edge of serial clock). At least one falling edge transition on SCLK is
needed whenever CS is brought high.
D Control via FS—The MSB is presented after the rising edge of FS. The falling edge of FS starts the cycle.
The MSB may be read on the first falling edge of SCLK after FS is low. This is the typical configuration when
the ADC is the only device on the DSP serial port.
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