LTC1099CSW Linear Technology, LTC1099CSW Datasheet - Page 11

• Manufacturer Part Number: LTC1099CSW
• Description: IC A/D CONV 8BIT HI-SPEED 20SOIC
• Manufacturer: Linear Technology

Specifications of LTC1099CSW

• Number Of Bits: 8
• Sampling Rate (per Second): 400k
• Data Interface: Parallel
• Number Of Converters: 3
• Power Dissipation (max): 55mW
• Voltage Supply Source: Single Supply
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (0.300", 7.50mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: LTC1099CS

N/C
ANALOG INTERFACE
APPLICATIONS
Analog Multiplier
The schematic Figure 9 shows the LTC1099 configured
with a DAC to form a two quadrant analog multiplier. An
input waveform is applied to the LTC1099 where it is
digitized at a 300kHz rate. The digitized signal is fed to the
DAC in “flow-through” mode where another signal is input
to the DAC reference input. In this way, the two analog
signals are multiplied to produce a double sideband ampli-
tude modulated output. Figure 10 shows a 3kHz sine wave
multiplied by a 100Hz triangle.
U
3MHz
OSC
5V
OUT
5V
1
2
3
4
5
6
7
U
= ANALOG GROUND
= DIGITAL GROUND
CLK
N/C
74LS90
14
13
12
11
10
9
8
(V
10 = 300kHz
IN1
ANALOG
INPUT
) 0V TO 5V
15V
N/C
IN
CS AND RD LOW
10
1
2
3
4
5
6
7
8
9
IN
DB0
DB1
DB2
DB3
WR/RDY
MODE
RD
INT
GND
LT1019-5
LTC1099
AGND
GND
REF
TRIM
REF
DB7
DB6
DB5
DB4
OUT
CS
+
–
Figure 9
Figure 10
20
19
18
17
16
15
14
13
12
11
DB0-DB3
Note that since this is only a two quadrant multiplier, a
carrier component (the input to the LTC1099) will appear
in the output spectrum. Figure 11 shows the frequency
spectrum of a 42.5kHz sine wave multiplied by a 5kHz sine
wave. The depth of modulation is about 30dB. Figure 12
shows a 42.375kHz sine wave multiplied by a 30.875kHz
sine wave. Note that at these higher frequencies, the depth
of modulation is still about 30dB. The carrier feed-through
is seen in Figure 12.
4
25k
10 F
5V
5V
REF
0.01 F
4.7 F
(V
4
DB4-DB7
IN2
8
) +10V TO –10V
ANALOG
INPUT
1099 F10
MICROLINEAR
MP1208 DAC
V
TRIANGLE INTO LTC1099
~100Hz
V
INTO DAC ~ 3kHz
IN1
IN2
10
11
12
1
2
3
4
5
6
7
8
9
CS
WR1
GND
DI5
DI4
DI3
DI2
DI1
DI0
V
RFB
0V TO 5V
REF
4.8V SINE
8
BYTE 1/
BYTE 2
I
I
XFER
WR2
DI10
DI11
OUT2
OUT1
V
DI6
DI7
DI8
DI9
CC
10pF
24
23
22
21
20
19
18
17
16
15
14
13
LTC1099
+
–
12V
1
LT1056
–15V
5
10 F
50k
OFFSET NULL
15V
11
15V