Application Report
SBFA020– September 2011
Key Differences Between the PCM290xB and PCM290xC
.................................................................................................................. Audio Converter Products
ABSTRACT
This document presents the major differences between the PCM290xB and PCM290xC series audio data
converters.
Contents
1 Overview ..................................................................................................................... 1
2 Volume Control Behavior Change ........................................................................................ 1
3 Recording Level Control Behavior Change .............................................................................. 2
4 Design and End User Impact .............................................................................................. 4
1 Overview
The PCM290xC audio devices have been updated to pass the Microsoft
®
Windows
®
Logo Kit (WLK) v1.5.
This certification makes these converters fully compatible with the Windows 7
®
operating system. Previous
generation PCM290xB devices remain functionally compatible with Windows 7; however, manufacturers
cannot pass WLK tests with these devices, and therefore are not allowed to put the Microsoft Windows 7
logo on products that use the PCM290xB series.
Table 1 lists the descriptors that have been changed on the PCM290xC devices.
Table 1. Descriptor Differences Between the PCM290xB and PCM290xC Devices
Descriptor PCM290xB PCM290xC
Product ID 0x29B0/0x29B2/0x29B3/0x29B6 0x29C0/0x29C2/0x29C3/0x29C6
Vendor strings Burr-Brown from TI BurrBrown from Texas
Instruments
Product strings USB Audio CODEC USB AUDIO CODEC
Input terminal 0x0201 (Microphone) 0x0603 (Line connector)
As Table 1 indicates, the primary changes here are the vendor string, the product string, and the input
terminal.
2 Volume Control Behavior Change
The volume control panel in Windows actually changes gain on the PCM290xB device itself, rather than
allowing users to perform a simple digital mix with the operating system.
Microsoft, Windows, Windows 7 are registered trademarks of Microsoft Corporation.
All other trademarks are the property of their respective owners.
1
SBFA020–September 2011 Key Differences Between the PCM290xB and PCM290xC
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0
10
20
30
40
50
60
70
80
-
-
-
-
-
-
-
-
0 50 100 150 200 250 300 350 400 450 500
Volume Slider (Min Range to Max Range)
Min Max
Output (dB)
PCM2900B, WinXP
PCM2900B, Win7
PCM290xC, WinXP
PCM290xC, Win7
PLAYBACK LEVEL COMPARISON BY OPERATING SYSTEM
40
20
0
20
40
60
80
-
-
-
-
0 50 100 150 200 250 300 350 400 450 500
Volume Slider (Min Range to Max Range)
Min Max
Output (dB)
PCM2900B, Vista
PCM2900B, Win7
PCM290xC
(Vista and Win7)
RECORD LEVEL COMPARISON BY OPERATING SYSTEM
Recording Level Control Behavior Change
www.ti.com
In the transition from WindowsXP through Vista and Windows 7, changes were made to the behavior and
scale of the volume sliders. As a result, TI has now updated the volume control curves in the PCM290xC.
The revised graph is shown in Figure 1.
Figure 1. Playback Level Comparison of PCM290xB/290xC Devices by Operating System
In Windows 7, as a result of the smaller number of steps, a small change on the slider can have a drastic
effect on the output volume. With the previous generation PCM290xB devices, a single volume step in
Windows 7 can be as much as five steps in Windows XP. Therefore, the volume curve was changed to
compensate for this operating system change.
3 Recording Level Control Behavior Change
On the PCM290xB series, the Microphone is identified as the input terminal descriptor. Thus, even though
the PCM290xB does not provide a gain control function such as a programmable gain amplifier (PGA),
Vista and Windows 7 both automatically give a positive gain on the volume control panel. As a result, the
input signal will saturate at even slight recording volume increases. On the PCM290xC series, the Line
connector is identified as the input terminal descriptor; therefore, Vista and Windows 7 do not present any
positive gain on the volume control panel, and input signal saturation does not occur. The revised graph is
shown in Figure 2.
Figure 2. Recording Level Comparison of PCM290xB/290xC Devices by Operating System
2
Key Differences Between the PCM290xB and PCM290xC SBFA020– September 2011
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U002
RA001
1.5 k
3W ´
3
C003
1.0 Fm
C004
1.0 Fm
CN001
67068-0001
R003
22 W
R002
22 W
4
3
2
1
R001
1.5 kW
CN002
FFC–10BMEP1
C005
1.0 Fm
R005
1 MW
C009
18 pF
C010
18 pF
X001
12 MHz
4
5
U001
REG103GA
–A
C001
0.1 Fm
+
+
+
+
+
+
+
R004
Jumper
2 (R1)
2 (R1)
1 (S)
1
1 (S)
1
CN101
Stereo Mini-jack
YKB21-5274
CN102
Stereo Mini-jack
YKB21-5274
Adj
EN
3
GND
OUT
IN
1
2
C002
1.0 Fm
R007
13 kW
R006
27 kW
C006
1.0 Fm
C007
1.0 Fm
C008
1.0 Fm
3 (T)
3 (T)
+
C117
10 F/16 Vm
C118
10 F/16 Vm
+
D001
RB520S-30
(GND)
(D )
P
(D )
M
(V
)
BUS
S/PDIF Out
S/PDIF In
SEL1
SEL0
REG-V
CC
1
2
3
4
5
6
7
8
9
10
11
12
13
14
28
27
26
25
24
23
22
21
20
19
18
17
16
15
D+
D–
V
BUS
DGNDU
HID0
PCM2900C/02C/06C
HID1
HID2
SEL0
SEL1
V
CCI
AGNDC
V L
IN
V R
IN
V
COM
SSPND
V
DDI
DGND
DOUT
DIN
V
CCI
AGNDX
XTI
XTO
V
CCI
AGNDP
V
CCI
V L
OUT
V R
OUT
SW003
FT1D-2M
SW001
FT1D-2M
SW002
FT1D-2M
+
–
C101
10 F/16 Vm
R101
12 kW
C103
1800 pF
R103
3.9 kW
2
3
1
U101
OPA2353UA
1/2
R105
12 kW
C105
330 pF
4
R107
100 W
C107
10 F/16 Vm
+
–
C102
10 F/16 Vm
R102
12 kW
C104
1800 pF
R104
3.9 kW
6
5
7
U101
OPA2353UA
2/2
R106
12 k
W
C106
330 pF
8
R108
100 W
+
–
C112
1800 pF
R113
3.9 kW
6
5
U102
OPA2353UA
1/2
R111
12 kW
C110
330 pF
R115
18 kW
C114
10 F/16 Vm
C116
10 F/16 Vm
C108
10 F/16 Vm
R109
100 W
7
8
+
–
C113
1800 pF
R114
3.9 kW
2
3
U102
OPA2353UA
2/2
R112
12 kW
C111
330 pF
R116
18 kW
C115
10 F/16 Vm
C109
10 F/16 Vm
R110
100 W
1
4
See Note (1)
www.ti.com
Recording Level Control Behavior Change
3.1 Input Full-Scale
There is also an important notice that is required to pass WLK1.5 certification with the PCM290xC.
The PCM290xC series supports 0.6 ● V
CCI
(approximately 0.7 V
RMS
) input full-scale. However, WLK1.5
requires greater than 1-V
RMS
input full-scale level. Therefore, the input full-scale must be set to more than
1.0 V
RMS
by adjusting the external input buffer circuit shown in Figure 3. The recommended input resistors
(R115 and R116) are 18 kΩ instead of 12 kΩ. This difference results in a 3.5-dB attenuation at the
external input circuit.
(1) Recommended resistor values for R115 and R116: 18 kΩ.
Figure 3. PCM290xC-EVM Board Schematic
3
SBFA020– September 2011 Key Differences Between the PCM290xB and PCM290xC
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Design and End User Impact
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4 Design and End User Impact
The original volume curve was never published in the PCM290xB product data sheet, because most users
do not tend to dial in an exact amount of attenuation/gain. Users are more likely to slide the bar up and
down until they find a comfortable listening level.
Windows 7 users, on the other hand, now find the volume controls in the new operating system
significantly more sensitive and easier to use with the new volume control curves in the PCM290xC family
of devices.
Designers using multiple PCM290xB devices in the same product should make efforts to ensure they are
not mixing PCM290xC and non-C (that is, PCM290x) devices together; volume behavior varies between
these two generations of devices.
From the perspective of the PC Speaker and PC Accessory features, there should be little impact for end
users. They will continue to use the volume control sliders until they find a comfortable listening point.
However, systems that require specific input and output voltages may need to be reconfigured if the input
and output are attenuated from the typical 0-dB attenuation point in systems by default.
4
Key Differences Between the PCM290xB and PCM290xC SBFA020– September 2011
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