TLC5628C_15 Datasheet, PDF (3/17 Pages) Texas Instruments – OCTAL 8-BIT DIGITAL-TO-ANALOG CONVERTERS

TLC5628C, TLC5628I
OCTAL 8-BIT DIGITAL-TO-ANALOG CONVERTERS
SLAS089E – NOVEMBER 1994 – REVISED APRIL 1997
detailed description
The TLC5628 is implemented using eight resistor-string DACs. The core of each DAC is a single resistor with
256 taps, corresponding to the 256 possible codes listed in Table 1. One end of each resistor string is connected
to GND and the other end is fed from the output of the reference input buffer. Monotonicity is maintained by use
of the resistor strings. Linearity depends upon the matching of the resistor segments and upon the performance
of the output buffer. Since the inputs are buffered, the DACs always present a high-impedance load to the
reference sources. There are two input reference terminals; REF1 is used for DACA through DACD and REF2
is used by DACE through DACH.
Each DAC output is buffered by a configurable-gain output amplifier, that can be programmed to times 1 or times
2 gain.
On power up, the DACs are reset to CODE 0.
Each output voltage is given by:
+ VO(DACA|B|C|D|E|F|G|H) REF
CODE
256
) (1 RNG bit value)
where CODE is in the range 0 to 255 and the range (RNG) bit is a 0 or 1 within the serial control word.
Table 1. Ideal Output Transfer
D7 D6 D5 D4 D3 D2 D1 D0
00000000
00000001
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
01111111
10000000
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
11111111
OUTPUT VOLTAGE
GND
(1/256) × REF (1+RNG)
•
•
(127/256) × REF (1+RNG)
(128/256) × REF (1+RNG)
•
•
(255/256) × REF (1+RNG)
data interface
With LOAD high, data is clocked into the DATA terminal on each falling edge of CLK. Once all data bits have
been clocked in, LOAD is pulsed low to transfer the data from the serial input register to the selected DAC as
shown in Figure 1. When LDAC is low, the selected DAC output voltage is updated when LOAD goes low. When
LDAC is high during serial programming, the new value is stored within the device and can be transferred to
the DAC output at a later time by pulsing LDAC low as shown in Figure 2. Data is entered most significant bit
(MSB) first. Data transfers using two 8-clock cycle periods are shown in Figures 3 and 4.
CLK
DATA
LOAD
tsu(DATA-CLK)
tv(DATA-CLK)
tsu(LOAD-CLK)
A2
A1
A0 RNG D7
D6
D5
D4
D2
D1
D0
tsu(CLK-LOAD)
tw(LOAD)
Figure 1. LOAD-Controlled Update (LDAC = Low)
DAC Update
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