WM8310GEB/V Wolfson Microelectronics, WM8310GEB/V Datasheet - Page 96

• Manufacturer Part Number: WM8310GEB/V
• Description: POWER MANAGEMENT SUBSYSTEM, 169BGA
• Manufacturer: Wolfson Microelectronics

Specifications of WM8310GEB/V

• Supply Voltage: 7V
• No. Of Step-down Dc - Dc Converters: 4
• No. Of Ldo Regulators: 11
• Digital Ic Case Style: BGA
• No. Of Pins: 169
• No. Of Regulated Outputs: 13
• Operating Temperature Range: -40°C To
• Rohs Compliant: Yes
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

WM8310
16 CURRENT SINKS
16.1 GENERAL DESCRIPTION
16.2 CURRENT SINK CONTROL
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The WM8310 provides two Current Sinks, ISINK1 and ISINK2. These are programmable constant-
current sinks designed to drive strings of serially connected LEDs, including white LEDs used in
display backlight applications.
The WM8310 Boost Converter, DC-DC4, is designed as a power source for LED strings. Driving
LEDs in this way is particularly power efficient because no series resistor is required. The Boost
Converter can generate voltages higher than the Battery, Wall or USB supply, producing the
necessary combined forward voltages of long LED strings. See Section 15.15.3 for details of DC-
DC4 operation.
The configuration of the Current Sinks is described in the following sections.
16.2.1
In the ON power state, the Current Sinks ISINK1 and ISINK2 can be enabled in software using the
CS1_ENA and CS2_ENA register fields as defined in Table 48. When the Current Sinks are enabled,
the drive current is controlled by the CS1_DRIVE and CS2_DRIVE bits. Note that the Current Sinks
permit current flow only when the applicable CSn_ENA and CSn_DRIVE bits are both set.
The WM8310 Boost Converter, DC-DC4, is the recommended power source for the Current Sinks.
The recommended switch-on sequence is as follows:
•
•
The status of the Current Sinks in the SLEEP power state are controlled by CS1_SLPENA and
CS2_SLPENA, as described in Table 48. The Current Sinks may either be disabled in SLEEP or
remain under control of the applicable CSn_ENA register bit.
If a Current Sink is disabled in SLEEP, then the applicable CSn_DRIVE bit is automatically reset to 0
as part of the SLEEP transition sequence. Note that the CSn_DRIVE bit will remain reset at 0
following a WAKE transition; the Current Sink can only be re-enabled by writing to the applicable
CSn_DRIVE register bit.
If both Current Sinks are disabled in SLEEP, then DC4 can also be disabled in SLEEP, by setting
DC4_SLPENA = 0, as described in Section 15.4.2. If DC4 is not disabled, then it is important that
CSn_ENA also remains set in the SLEEP power state.
The recommended switch-off sequence for DC-DC4 and the Current Sinks is as follows:
•
•
•
Note that this switch-off sequence is important in order to avoid forward-biasing on-chip ESD
protection diodes.
Enable Current Sink and Current Drive (CSn_ENA = 1; CSn_DRIVE = 1)
Enable Boost Converter (DC4_ENA = 1)
Disable Current Drive (CSn_DRIVE = 0)
Disable Boost Converter (DC4_ENA = 0)
Disable Current Sink (CSn_ENA = 0)
ENABLING THE SINK CURRENT
PP, December 2009, Rev 3.0
Pre-Production
96