LTC1450LCG Linear Technology, LTC1450LCG Datasheet - Page 13

• Manufacturer Part Number: LTC1450LCG
• Description: IC D/A CONV 12BIT R-R PAR 24SSOP
• Manufacturer: Linear Technology

Specifications of LTC1450LCG

• Settling Time: 14µs
• Number Of Bits: 12
• Data Interface: Parallel
• Number Of Converters: 1
• Voltage Supply Source: Single Supply
• Power Dissipation (max): 750µW
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 24-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

TYPICAL APPLICATIONS
4-Quadrant Multiplying DAC Application
This application shows the LTC1450L configured as a
single supply 4-quadrant multiplying DAC. It uses a 5V
supply and only one external component, a 5k resistor tied
from REFOUT to ground. (The LTC1450 can be used in a
similar fashion.) The multiplying DAC allows the user to
digitally change the amplitude and polarity of an AC input
signal whose voltage is centered around an offset signal
ground provided by the 1.22V reference voltage. The
transfer function is shown in the following equations.
For the LTC1450L Gain = 2.05 and V
Table 1 shows the expressions for V
V
2.3V
output waveforms for zero-scale and full-scale DAC codes.
IN
V
V
, V
OUT
OUT
P-P
REF
triangle wave input signal and the corresponding
= (V
= (V
and D
IN
IN
– 1.22V)
– V
IN
REF
. The scope photo shows a 12.5kHz,
)
Internal Reference, REFLO/REFHI Pins, Gain Adjust and Wide Supply Voltage Range
Gain
2.05
D
IN
4096
4096
D
WR
CSMSB
CSLSB
LDAC
CLR
D
IN
IN
U
– 1
Allow 4-Quadrant Mulitplying on a 5V Single Supply
– 1.05
BUFFERED
REF
OUT
LATCHES
POWER-ON
DOUBLE-
DAC
RESET
+ 1
N
= 1.22V
as a function of
+ V
+ 1.22V
1.22V 1.15V
REFOUT
REF
REFERENCE
V
1.22V
IN
12-BIT
DAC
5k
REFLO
REFHI
V
REF
Table 1. Binary Code Table for 4-Quadrant, Multiplying DAC
Application
1.22V 1.15V
1111 1111 1111
1100 0001 1001
1000 0011 0010
0100 0100 1011
0000 0110 0100
0000 0000 0000
MSB
BINARY DIGITAL
AT 12.5kHz
INPUT CODE IN
DAC REGISTER
D
Waveforms for Zero-Scale and Full-Scale DAC Settings
IN
X1/X2
Clean 4-Quadrant Multiplying Is Shown in the Output
D
= 4095
IN
R
V
V
OUT
OUT
V
= 0
IN
1.05R
LSB
–
+
GND
V
5V
CC
ANALOG OUTPUT (V
(4094/4096)(V
0.5(V
V
– 0.5(V
– 1.0(V
– 1.05(V
REF
LTC1450L
LTC1450/LTC1450L
1450/50L TA07
IN
IN
IN
– V
IN
20 s/DIV
– V
– V
– V
REF
REF
REF
REF
) + V
IN
) + V
) + V
V
1.22V 1.21V
– V
) + V
OUT
REF
REF
REF
REF
OUT
REF
) + V
)
REF
1450/50L TA08
2V/DIV
1V/DIV
1V/DIV
13