Specifications

ESS Technology, Inc. SAM0023-122898 77
ES1869 DATA SHEET
POWER MANAGEMENT
Pop Prevention in the External Amplifier
Normally, to directly drive speakers in an ES1869 design,
an external stereo amplifier chip is used. There are two
power management problems associated with an external
amplifier:
1. The amplifier itself draws current unless it can be
powered down.
2. Suspend/resume causes pops because power is
removed from the ES1869 and then re-applied.
Amplifiers such as the SGS/Thomson TDA7233 have a
mute input which reduces current to 400 microamps and
also reduces pops from the suspend/resume process.
This part is a mono amplifier, so two are required. Connect
GPO0 to the active-low MUTE input of the TDA7233. In
this case the amplifier is muted after hardware reset.
During start-up, program the ES1869 so that GPO0 is high
when powered-up and low when fully powered-down.
Program a delay of about 133 milliseconds between
power-down and power-up states, before GPO0 returns
high, to allow the ES1869 analog circuits to stabilize.
Power Management and the FM Synthesizer
The ES1869 FM synthesizer is a fully static design. This
means that the clock can be stopped to power-down the
circuitry without loss of the state. For suspend/resume
applications, the entire context of the synthesizer can be
read back.
Self-Timed Power-Down
The ES1869 microcontroller can be programmed to monitor
I/O activity in place of the system processor, and after a
programmable period of inactivity, enter either a partial or full
power-down state.
In self-timed power-down, power is maintained as for partial
or full power-down, except the decision to power-down is
made by the ES1869 itself. The ES1869 microcontroller
waits for a pre-programmed period of I/O inactivity between
successive commands before entering partial or full power-
down state.
The ES1869 requires use of the activity flags in register
Audio_Base+6h. Therefore, if this feature is enabled, the
system processor cannot monitor I/O activity.
Enabling Self-Timed Power-Down
1. Send command C6h to enable access to the controller
registers.
2. Send command BDh.
3. Send the time out value N, where the time period is N
x 8 seconds. If the value N is zero, self-timed power-
down is disabled.
4. Send command C7h to disable access to the controller
registers.
Whether the ES1869 enters partial or full power-down is
determined by bit 3 of port Audio_Base+7h.
Even if self-timed power-down is enabled, the ES1869 can
be commanded to power-down by bit 2 of port
Audio_Base+7h.
There is one limitation to this feature. The timing of
inactivity only occurs between commands sent to the
ES1869. A program may leave the ES1869 in a state
where timing will not happen, such as if it exits without
completion of a DMA transfer. However, most programs
will leave the ES1869 with appropriate registers defined.
General-Purpose Outputs and Power-Down
The ES1869 has the ability to have one or both of the
general-purpose outputs GPO0 and GPO1 change state
when the ES1869 is powered-down.
After hardware reset, this feature is disabled and the
general-purpose outputs are not affected by power-down.
A controller register in the ES1869 must be programmed to
enable this feature. Specifically, the GPO Power-Down
Control register is set by writing the command CFh to port
Audio_Base+Ch followed by the data. To read the GPO
Power-Down Control register write the command CEh to
Audio_Base+Ch and read the data from port
Audio_Base+Ah. This register should be set once by
system software after system reset. This register is
unaffected by soft resets. Using this register, one or both of
the general-purpose outputs can be programmed to be
inverted from their normal state during power-down. The
normal state of each pin is set by the appropriate bits 1:0 of
port Audio_Base+7h. A further feature allows the inverted
outputs to return to their normal state immediately after
power-up or after a programmed delay after power-up.
GPO Power-Down Register
On reset, this register assumes the value of 00h. This
means that GPO0 and GPO1 are unaffected by the power-
down status; that is, they remain in the state programmed
into port Audio_Base+7h.
NOTE: “Power-down” as used in this document refers to
full power-down, i.e., when both the analog and digital
parts of the ES1869 are powered-down.
Restore
GPO1 timed
Invert GPO1
at PDN
Restore
GPO0 timed
Invert GPO0
at PDN
0 T2 T1 T0
7 6 5 4 3 2 1 0