Datasheet

LTC6602
24
6602fc
APPLICATIONS INFORMATION
Figure 18. Filter Transient Response to a Tag Symbol Sequence
detecting the symbol sequence (in an RFID environment,
noise will be superimposed on the output signal). In
general, increasing the lowpass f
CUTOFF
and/or decreasing
Figure 17. An Adaptable RFID Baseband Filter with SPI Control
6602 F17
LTC6602
V+
IN
+INA
–INA
+INB
–INB
R
BIAS
V
OCM
MUTE
GAIN0(D0)
GAIN1
GND
GND
–OUTA
+OUTA
–OUTB
+OUTB
CLKIO
SER
CLKCNTL
HPFO(SDO)
HPFI(SDI)
LPFO(SCLK)
LPF1(CS)
V+
A
V+
D
68.1k
0.1µF 0.1µF
5V 3V
1 2 16
24 18
19
12
13
15
17
5
9
6
11
10
23
7
8
4
3
20
21
22
14
25
CS1 CS2SCK SDI
SPI CONTROL OF LTC6602
SETS THE FILTER GAIN AND THE
LOWPASS AND HIGHPASS
DIVISION RATIO
0.1µF
174k
3V
CS
SCLK
SDI
V
OUT
GND
V
+
I CHANNEL INPUT
Q CHANNEL INPUT
I CHANNEL OUTPUT
Q CHANNEL OUTPUT
SPI CONTROL OF DAC
SETS THE LTC6602
CLOCK FREQUENCY
40MHz TO 100MHz
6
5
4
1
2
3
TRANSMITTER MUTE INPUT
ADC VCOM INPUT
LTC2630
8-BIT DAC
DAC V
OUT
RANGE 0V TO 2.5V
(USING THE LTC2630
INTERNAL REFERENCE)
3V
0.1µF
the highpass f
CUTOFF
“enhances” signal transitions and
intervals and increases filter output noise.
(µs)
(a)
6602 F19a
0 10 20 30 40 50 60 70 80 90 100110120
TYPICAL TAG
SYMBOL
SEQUENCE
100kHZ
LOWPASS
LOWPASS ONLY FILTER
6602 F19b
(µs)
(b)
0 10 20 30 40 50 60 70 80 90 100110120
100kHz LOWPASS + 30kHz HIGHPASS FILTER
6602 F19c
(µs)
(c)
0 10 20 30 40 50 60 70 80 90 100110120
100kHz LOWPASS + 10kHz HIGHPASS FILTER