LTC1564C View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1564C' PDF : 12 Pages View PDF
LTC1564
PI FU CTIO S
passes the bits directly when the CS/HOLD input is at logic
0. When CS/HOLD changes to logic 1, the F pins cease to
have effect and the latch holds the previous values. The F
code controls the filter’s cutoff frequency fC in 10kHz steps
up to 150kHz, as summarized in Table 1.
Table 1
F3 F2 F1 F0
NOMINAL FC
(AT OUTPUT OF INTERNAL LATCH) (CUTOFF FREQUENCY)
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
0 (Mute State: Filter Gain is Zero)
10kHz
20kHz
30kHz
40kHz
50kHz
60kHz
70kHz
80kHz
90kHz
100kHz
110kHz
120kHz
130kHz
140kHz
150kHz
Thus fC is proportional to the binary value of the F code.
Note that small current sources pull F1 to V+ and F3, F2
and F0 to V– when these pins are left unconnected (see
Electrical Characteristics, Note 5). This sets an F code
input of 0010 (2, in decimal form) by default, giving an fC
of 20kHz in normal filtering operation, if CS/HOLD is logic
0 or is open circuited.
G0, G1, G2, G3 (Pins 9, 10, 11, 12): CMOS-Level Digital
Gain Control (“G Code”) Inputs. G3 is the most significant
bit (MSB). These pins program the LTC1564’s passband
gain through the internal latch, which passes the bits
directly when the CS/HOLD input is at logic 0. When
CS/HOLD changes to logic 1, the G pins cease to have
effect and the latch retains the previous input values. This
gain control is linear in amplitude: nominal passband gain
of the LTC1564 is the binary value of the G code, plus one
as shown in Table 2.
Note that small current sources pull the G pins to V – when
these pins are left unconnected (see Electrical Character-
istics, Note 5). This sets a G code input of 0000 by default,
giving unity passband gain in normal filtering operation, if
CS/HOLD is logic 0 or is open circuited.
RST (Pin 13): CMOS-Level Asynchronous Reset Input.
Logic 0 on this pin immediately resets the internal F and G
latch to all zeros, regardless of the state of the CS/HOLD
pin or the F or G input pins. This causes the LTC1564 to
enter a mute state (powered but with zero signal gain)
because of the resulting F = 0000 command. Logic 1
permits the other pins to control F and G. This pin floats to
logic 1 (V+) when open circuited because of a small
current source (see Electrical Characteristics, Note 5). A
brief internal reset (shorter than the analog settling time of
the filter) also occurs when power is first applied.
Table 2
G3 G2 G1 G0
(AT OUTPUT OF INTERNAL LATCH)
0
0
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
1
1
NOMINAL
PASSBAND GAIN
(VOLT/VOLT) (dB)
1
0
2
6.0
3
9.5
4
12
5
14.0
6
15.6
7
16.9
8
18.1
9
19.1
10
20.0
11
20.8
12
21.6
13
22.3
14
22.9
15
23.5
16
24.1
MAXIMUM INPUT SIGNAL LEVEL
(VOLTS PEAK-TO-PEAK)
DUAL 5V SINGLE 5V SINGLE 3V
10
5.0
3.0
5
2.5
1.5
3.33
1.67
1.0
2.5
1.25
0.75
2
1
0.6
1.67
0.83
0.5
1.43
0.71
0.43
1.25
0.63
0.38
1.1
0.56
0.33
1.0
0.50
0.30
0.91
0.45
0.27
0.83
0.42
0.25
0.77
0.38
0.23
0.71
0.36
0.21
0.67
0.33
0.20
0.63
0.31
0.19
NOMINAL
INPUT IMPEDANCE
(kΩ)
10
5
3.33
2.5
2
1.67
1.43
1.25
1.11
1
0.91
0.83
0.77
0.71
0.66
0.63
6
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