WM8311GEB/V Wolfson Microelectronics, WM8311GEB/V Datasheet - Page 283

• 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
30.4 DC-DC (STEP-UP) CONVERTER EXTERNAL COMPONENTS
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The recommended connections to the DC-DC (Step-Up) Converter are illustrated in Figure 42.
Figure 42 DC-DC (Step-Up) Converters External Components
In the constant current mode, the DC-DC Converter output voltage is controlled by the WM8311 in
order to achieve the required current in ISINK1 or ISINK2. The required current is set by the
CSn_ISEL register fields, as described in Section 16.2.2. A typical application for this mode would be
a white LED driver, where several LEDs are connected in series to achieve uniform brightness.
The DC-DC (Step-Up) Converter is capable of generating output voltages of up to 30V. The
maximum output voltage is determined by the two external resistors R1 and R2, which form a
resistive divider between load connection and the voltage feedback pin DC4FB. The maximum output
voltage is set as described in the following equation:
Setting R2 to 47kΩ is recommended for most applications; R1 can be calculated using the following
equation, given the required output voltage:
Note that the resistors determine the maximum output voltage. The actual voltage will be determined
by the selected ISINK current, subject to the device limits.
When selecting a suitable capacitor, is it imperative that the effective capacitance is within the
required limits at the applicable input/output voltage of the converter. Ceramic X7R or X5R types are
recommended.The choice of output capacitor for DC-DC4 varies depending on the required output
voltage. See Table 117 for further details.
DC4_FBSRC = 0 (ISINK1)
DC4_FBSRC = 1 (ISINK2)
2.7V – 5.5V
DC4VDD
WM8311
DC-DC4
C
IN
DC4LX
DC4GND
ISINKn
DC4FB
L
C
OUT
V
O
PP, December 2009, Rev 3.0
R1
R2
WM8311
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