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WM8980CGEFL/V データシート(PDF) 68 Page - Wolfson Microelectronics plc |
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WM8980CGEFL/V データシート(HTML) 68 Page - Wolfson Microelectronics plc |
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68 / 123 page  WM8980 Pre-Production w PP, Rev 3.8, May 2012 68 ENABLING THE OUTPUTS Each analogue output of the WM8980 can be separately enabled or disabled. The analogue mixer associated with each output has a separate enable. All outputs are disabled by default. To save power, unused parts of the WM8980 should remain disabled. The SLEEP bit should only be set on to reduce residual device currents once all the other power management bits have been set to off. Outputs can be enabled at any time, but it is not recommended to do so when BUFIO is disabled (BUFIOEN=0) or when BUFDCOP is disabled (BUFDCOPEN=0) when configured in output boost mode, as this may cause pop noise (see “Power Management” and “Applications Information” sections). REGISTER ADDRESS BIT LABEL DEFAULT DESCRIPTION R1 Power Management 1 2 BUFIOEN 0 Unused input/output tie off buffer enable 6 OUT3MIXEN 0 OUT3 mixer enable 7 OUT4MIXEN 0 OUT4 mixer enable 8 BUFDCOPEN 0 Output stage 1.5xAVDD/2 driver enable R2 Power Management 2 8 ROUT1EN 0 ROUT1 output enable 2 7 LOUT1EN 0 LOUT1 output enable 2 6 SLEEP 0 0 = normal device operation 1 = residual current reduced in device standby mode R3 Power Management 3 2 LMIXEN 0 Left mixer enable 3 RMIXEN 0 Right mixer enable 4 VBUFEN 0 Video buffer enable 5 ROUT2EN 0 ROUT2 output enable 2 6 LOUT2EN 0 LOUT2 output enable 2 7 OUT3EN 0 OUT3 enable 2 8 OUT4EN 0 OUT4 enable 2 Table 50 Output Stages Power Management Control Notes: All “Enable” bits are 1 = ON, 0 = OFF Disabling the outputs does not automatically mute the output mixers. To avoid pop noise, it is recommended that the relevant mixer is muted before disabling outputs. THERMAL SHUTDOWN The speaker outputs can drive very large currents. To protect the WM8980 from overheating a thermal shutdown circuit is included. The thermal shutdown can be configured to produce an interrupt when the device reaches approximately 125 oC. See General Purpose Input/Output section. REGISTER ADDRESS BIT LABEL DEFAULT DESCRIPTION R49 Output control 1 TSDEN 1 Thermal Shutdown Enable 0 : thermal shutdown disabled 1 : thermal shutdown enabled Table 51 Thermal Shutdown UNUSED ANALOGUE INPUTS/OUTPUTS Whenever an analogue input/output is disabled, it remains connected to a voltage source (either AVDD/2 or 1.5xAVDD/2 as appropriate) through a resistor. This helps to prevent pop noise when the output is re-enabled. The resistance between the voltage buffer and the output pins can be controlled using the VROI control bit. The default impedance is low, so that any capacitors on the outputs can charge up quickly at start-up. If a high impedance is desired for disabled outputs, VROI can then be set to 1, increasing the resistance to about 30k . |
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