wm8400 Wolfson Microelectronics plc, wm8400 Datasheet - Page 147

• Manufacturer Part Number: wm8400
• Description: Wolfson Audioplustm Hi-fi Audio Codec And Power Management Unit For Mobile Multimedia
• Manufacturer: Wolfson Microelectronics plc

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Pre-Production
DC-DC CONVERTER OPERATION
OVERVOLTAGE PROTECTION
When inductive components are connected to the Converters or Regulators, it is possible that
voltage overshoot can occur during load or line transitions. The WM8400 provides overvoltage
protection circuitry on the DC-DC Converters which minimizes these effects. When enabled, the
overvoltage protection aims to limit the transient voltage at 50mv above the selected level. This
feature is enabled using the register bits described in Table 94.
Table 94 DC-DC Converter Overvoltage Control
The WM8400 provides two DC-DC switching Buck Converters. These are versatile, step-down, PWM
controlled converters, designed to deliver high efficiency across all load conditions up to 600mA.
They are typically suitable for powering Digital Core and I/O functions. Their principal characteristics
are summarised in Table 95.
Table 95 DC-DC Converter Characteristics
The connections to the Converter DC1 are illustrated in Figure 85. The equivalent circuit applies to
DC Converter 2 also.
Figure 85 DC-DC Converter Connections
The external components at the converter output are required by the DC-DC Converter integral loop
compensation circuit. Note that the recommended output capacitor Cout varies according to the
required transient response on each DC-DC Converter. See “Applications Information” for details of
the recommended external components.
R70 (46h)
R72 (48h)
Converter Type
Input Voltage Range
Output Voltage Range
Maximum Load Current
Switching frequency
REGISTER
ADDRESS
PARAMETER
BIT
7
7
DC1_OV_PROT
DC2_OV_PROT
LABEL
Buck Converter
2.7V to 5.5V
0.85V to 4.025V (performance only measured to 3.4V)
600mA (short term output up to 1000mA is possible)
2.048MHz
DEFAULT
0b
0b
DC1 Overvoltage Protection
0 = Disabled
1 = Enabled
DC2 Overvoltage Protection
0 = Disabled
1 = Enabled
VALUE
DESCRIPTION
PP, April 2009, Rev 3.0
WM8400
147