WM9705SEFT/RV Wolfson Microelectronics, WM9705SEFT/RV Datasheet - Page 50

• Manufacturer Part Number: WM9705SEFT/RV
• Description: Audio CODECs Stereo AC'97 Codec T/P Interface
• Manufacturer: Wolfson Microelectronics

Specifications of WM9705SEFT/RV

• Number Of Adc Inputs: 1
• Number Of Dac Outputs: 1
• Conversion Rate: 48 KSPs
• Interface Type: AC97
• Resolution: 12 bit
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: TQFP-48
• Minimum Operating Temperature: - 25 C
• Number Of Channels: 2 ADC, 2 DAC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

WM9705
STANDBY OPERATION AND WAKE-UP
w
Table 29 Pen Detect Comparator Threshold
Figure 25 shows the pen detection function schematically.
Figure 25 Pen Detection Configuration
WM9705 allows for complete zero power standby operation, and wake-up-on-pen-down.
That is, all features of the device can be put into zero quiescent current standby, including the
digital interfaces, and the device will wait consuming near zero power until it is re-awoken via pen
down event or via activity on the AC link.
The AC link interface specification allows for standby operation, with all clocks stopped and the
oscillator powered down, (all PR bits set). From this state, either the controller or the Codec can
re-awaken the AC link. This feature is used by WM9705 to allow the standby operation, and wake
on pen down function.
Once in standby, (all PR bits set and Pen digitiser power down control bits PRP{1:0] in reg 78h
set to), the device awaits detection of pen down. Once this occurs, PRP[1] is set to active (1) and
the pen digitiser wakes up, toggles the PENDET pin, and wakes the AC link by toggling the
SDATAIN line. It is then up to the link controller how to respond. It will then toggle the SYNC
signal, which causes the codec to wake up the AC link by re-setting PR4, waking the oscillator
and starting to send BITCLKs. If RPR is set then pen down will also automatically reset PR4 and
wake up the codec.
If the PRP[1:0] is set to 10, then the device is NOT woken on pen down detect, but the PENDET
flag is toggled on pin 46 when the pen is detected as ‘down’. The controller may then wake up the
AC link and hence set PRP[1] bit if it so wishes.
0000
0001
0010
0011
0100
0101
0110
0111
PDD[3-0]
Xswn
X-
X+
Rpen
Use zero power comp.
Vmid/15
2Vmid/15
3Vmid/15
4Vmid/15
5Vmid/15
6Vmid/15
7Vmid/15
Yswp
Y+
Y-
PEN DETECT
THRESHOLD
4 bit
Rpusw
Rpu
setting DAC
Pen detect
threshold
1000
1001
1010
1011
1100
1101
1110
1111
PDD[3-0]
zero power comparator
precision comparator
8Vmid/15
9Vmid/15
10Vmid/15
11Vmid/15
12Vmid/15
13Vmid/15
14Vmid/15
Vmid
PEN DETECT
THRESHOLD
mux
sel
PD Rev 4.5 July 2008
Production Data
PENDET
50