DA7218 datasheet(57/198 Pages) RENESAS

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DA7218

Ultra-Low Power Stereo Codec

Datasheet

Revision 3.4

24-Dec-2021

CFR0011-120-00

57 of 197

9.4.6

Charge Pump Control

The charge pump is enabled by asserting cp_en in the CP_CTRL register. Once enabled, the charge

pump can be controlled manually or automatically. When under manual control (cp_mchange = 00),

the output voltage level is directly determined by cp_mod.

The amount of charge stored, and therefore the voltage generated, by the charge pump is controlled

by the charge pump controller. As the power consumed by devices such as amplifiers is proportional

to v

oltage, significant power savings are available by matching the charge pump’s output with the

system’s power requirement.

Under automatic control, there are three modes of operation that are determined by the cp_mchange

setting. All four modes (one manual and three automatic) are described in Table 43.

Table 43: Charge Pump Output Voltage Control

Charge Pump

Tracking Mode

cp_mchange

Charge Pump Output Voltage

Details

Manual

The charge pump’s output voltage is determined by

the settings of cp_mod

Voltage level depends on the

programmed gain setting

The charge pump controller monitors the PGA

volume settings and generates the minimum voltage

that is required to drive a full-scale signal at the

current gain level

Voltage level depends on the DAC

signal envelope

The charge pump controller monitors the DAC

signal, and generates the voltage that is required to

drive a full-scale output at the current DAC signal

volume level

Voltage level depends on the signal

magnitude and the programmed

gain setting

The charge pump monitors both the programmed

volume settings and the actual signal size, and

generates the appropriate output voltage

This is the most power-efficient mode of operation

When cp_mchange is set to 10 (tracking DAC signal size, described in Table 43) or cp_mchange is

set to 11 (tracking the output signal size), the charge pump switches its supply between the VDD rail

and the VDD/2 rail depending on its power requirements. When low output voltages are needed, the

charge pump saves power by using the lower-voltage VDD/2 rail.

The switching point between using the VDD rail and the VDD/2 rail is determined by the

cp_thresh_vdd2 register setting. The switching points determined by cp_thresh_vdd2 vary between

the two cp_mchange modes, and are summarized Table 44 and Table 45.

Table 44: cp_thresh_vdd2 Settings in DAC Signal Tracking Mode (cp_mchange = 10)

cp_thresh_vdd2 Setting

Approximate Switching Point

Notes

0x01

-30 dBFS

Do not use. Very power-inefficient as

nearly always VDD/1

0x03

-24 dBFS

Not recommended. Very power-inefficient

as nearly always VDD/1

0x07

-18 dBFS

May be used but not power efficient

0x0E

-12 dBFS

May be used

0x10

-10 dBFS

Recommended setting

0x3F to 0x13

Reserved, do not use

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