DA7212 datasheet(39/129 Pages) DIALOG

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DA7212

Ultra-low power stereo codec

Company confidential

Datasheet

Revision 3c

24-Nov-2015

39 of 129

13.16 Charge pump clock control

The charge pump on DA7212 requires two clocks (cp_clk and cp_clk2). The cp_clk2 clock runs at a

slower frequency than cp_clk. It is cp_clk that actually clocks the charge pump.

To prevent the clocks stopping in an unknown state, there are always two pulses on cp_clk for every

one pulse of cp_clk2. This is illustrated in Figure 12.

cp_clk

clk

cp_clk2

Figure 12: Input (clk) and output clocks (cp_clk and cp_clk2) at CP_FCONTROL = 010

When CP_ANALOGUE_LVL = 00 (‘No feedback’ – see Section 13.17 for more details), the charge

pump’s nominal clock rate cp_clk is controlled by CP_FCONTROL, providing a range from 1 MHz

(CP_FCONTROL = 000) down to 63 kHz (CP_FCONTROL = 100). With the slower clock rates,

quiescent power consumption is lower but the trade-off is a reduced load current, and slower

changes to the voltage.

Section 13.17 describes how quiescent power and load current can be varied according to demand.

13.17 Boosting the charge pump using demand feedback control

When CP_ANALOGUE_LVL = 00, the clock frequency for the charge pump is under direct control of

the registers as described in Table 29.

When CP_ANALOGUE_LVL = 01 or 10 (11 is reserved and is not used), the demands on the charge

pump output are tracked, and the clock frequency is boosted when necessary to give the required

output current.

This gives the benefit of a very low (or even zero) quiescent current when the charge pump is not

required combined with a maximum output when that is required.

13.17.1 Tracking the demands on the charge pump output

There are three points at which the demands on the charge pump can be tracked. These tracking

points are determined by CP_MCHANGE.

13.17.1.1

CP_MCHANGE = 00 (manual mode)

If CP_MCHANGE = 00, the voltage level is controlled by the CP_MOD setting.

13.17.1.2

CP_MCHANGE = 01 (tracking the PGA gain setting)

If CP_MCHANGE = 01, it is the PGA gain setting that is tracked, and which provides the feedback to

boost the clock frequency when necessary.

13.17.1.3

CP_MCHANGE = 10 (tracking the DAC signal setting)

If CP_MCHANGE = 01, it is the size of the DAC signal that is tracked, and which provides the

feedback to boost the clock frequency when necessary.

13.17.1.4

CP_MCHANGE = 11 (tracking the output signal magnitude)

If CP_MCHANGE = 01, it is the magnitude of the output signal that is tracked, and which provides

the feedback to boost the clock frequency when necessary.

DA7212 Datasheet(PDF) 39 Page - Dialog Semiconductor

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