that4315 THAT Corporation, that4315 Datasheet - Page 9

• Manufacturer Part Number: that4315
• Description: Pre-trimmed Low-voltage Low-power Analog Engine
• Manufacturer: THAT Corporation

Document 600065 Rev 04
pre/de-emphasis to the signal path.
helps overcome the “aqua” characteristics of the FM
RF channel by raising the level of the higher fre-
quency portion of the signal while it is in the trans-
mission channel. The de-emphasis in the decoder
brings the frequency response of the signal back to
flat while simultaneously lowering the noise floor of
the channel.
This helps the system respond to impulse signals
that are accentuated by the signal pre-emphasis,
and result in a superior swept sine response.
RMS pre-emphasis is added to both detectors.
Decode In
Encode In
5
6
Vcc
Op-Amp
5
6
THAT Corporation; 45 Sumner Street; Milford, Massachusetts 01757-1656; USA
U4B
Op-Amp
U2B
Tel: [phone]; Fax: [phone]; Web: www.thatcorp.com
C10
100n
7
7
8
C12
V+
V-
1u
4
Op-Amp
1u
C1
U2C
C18
22n
4n7
C7
Pre-emphasis
C9
100n
Copyright © 2009, THAT Corporation
2k49
R10
1k15
21k0
R11
R1
Figure 7. Hifi 2:1 Decoder circuit
Figure 6. Hifi 2:1 encoder circuit
C11
1u
2k32
R3
V+
Gnd
Vcc
9
8
C14
10u
Vref
7
2
Filt
6
U3B
THAT4315
133k
R8
RMS In
Vcc
C6
22u
15
U1C
THAT
4315
C4
10u
4
VCA In
RMS Out
CT
482k
R12
R13
5k
C21
220p
EC+
EC-
C13
10u
11
12
tector is demonstrated.
level tracking in situations where one detector per-
forms substantially better than specified.
Encoder
the aforementioned improvements.
path, there is a static gain at low frequencies of
16 dB;
VCA Out
5
5
15
THAT4315
U1A
RMS Out
10u
C3
Additionally, a means to “floor out” the RMS de-
The encoder shown in Figure 6 implements all of
A
C16
22u
VCA In
482k
V
R6
CT
RMS In
=
13
EC+
EC-
4
Vref
Filt
133
21
6
11
12
7
U1B
THAT4315
VCA Out
U3A
THAT4315
k
k
Gnd
W
Vcc
2
W
9
8
@
THAT
4315
U3C
6 3
1k15
13
.
R5
2
3
133k
22p
C5
R2
2k49
U2A
R4
Op-Amp
2
3
22n
C8
1
100n
2k32
21k0
C19
U4A
R9
R7
Op-Amp
This helps improve low
1
C15
22p
8
C2
1u
C17
V+
4n7
V-
Op-Amp
4
U4C
Encode Out
Decode Out
In the signal
V+
C20
100n
Page 9