WM8311GEB/V Wolfson Microelectronics, WM8311GEB/V Datasheet - Page 47

• Manufacturer Part Number: WM8311GEB/V
• Description: POWER MANAGEMENT SUBSYSTEM, 121BGA
• Manufacturer: Wolfson Microelectronics

Specifications of WM8311GEB/V

• Supply Voltage: 5.5V
• No. Of Step-down Dc - Dc Converters: 4
• No. Of Ldo Regulators: 7
• Digital Ic Case Style: BGA
• No. Of Pins: 121
• No. Of Regulated Outputs: 9
• Operating Temperature Range: -40°C To
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Pre-Production
13.2 CRYSTAL OSCILLATOR
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Table 16 Clocking Control
The crystal oscillator generates a 32.768kHz reference clock, which is used to provide reference
clock for the Real Time Clock (RTC) in the WM8311. It may also be used as a reference input to the
FLL, for the purpose of generating other clocks. The oscillator requires an external crystal on the XTI
and XTO pins, as well as two capacitors, connected as shown in Figure 17.
Figure 17 Crystal Oscillator
A suitable crystal oscillator should be selected in accordance with the following requirements:
Table 17 Selection of Crystal Oscillator Component
The load capacitors C1 and C2 should be selected according to the recommended load capacitance,
C
Assuming C1 = C2 and C
For example, if the crystal has a load capacitance C
If a suitable 32.768kHz clock is already present elsewhere in the system, it is possible for the
WM8311 to use that external clock instead. The external clock should be applied to pin XTI, and the
XTO pin left floating in this case.
L
Norminal frequency
Series resistance
Maximum driving level
of the crystal, which is given by the following equation:
ADDRESS
C1 = C2 = 2 x (C
PARAMETER
BIT
STRAY
L
- 2.75pF).
= 2.75pF (typical pad i/o capacitance), then:
LABEL
MIN
0.5
50
32.768
DEFAULT
L
= 9pF, then C1 = C2 = 12.5pF.
MAX
70
0 = RTC unclocked in BACKUP
1 = RTC maintained in BACKUP
(Note that XTAL_ENA must also
be set if the RTC is to be
maintained in BACKUP.)
PP, December 2009, Rev 3.0
UNITS
DESCRIPTION
kHz
μW
kΩ
WM8311
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