CS47L85 datasheet(335/370 Pages) CIRRUS

335 / 370 page

CS47L85

Rev 4.3

335

CHARGE PUMPS, REGULATORS AND VOLTAGE REFERENCE

The CS47L85 incorporates two Charge Pump circuits and two LDO Regulator circuits to generate supply rails for internal

functions and to support external microphone requirements. The CS47L85 also provides four MICBIAS generators which

provide low noise reference voltages suitable for biasing electret condenser (ECM) type microphones or powering digital

microphones.

Refer to the

“Applications Information” section for recommended external components.

The CPVDD domain (1.8V) powers the Charge Pump 1 and Charge Pump 2 circuits. The CPVDD2 power domain (1.2V) is

an additional supply used by Charge Pump 1 only.

The DCVDD domain (1.2V) can be supplied externally, or can be provided by the LDO1 Regulator.

Note that the CPVDD2 domain must always be powered externally; the CPVDD2 domain should not be connected to the

LDO1 output.

CHARGE PUMPS AND LDO2 REGULATOR

Charge Pump 1 (CP1) is used to generate the positive and negative supply rails for the analogue output drivers. CP1 is

enabled automatically by the CS47L85 when required by the output drivers.

Charge Pump 2 (CP2) powers LDO2, which provides the supply rail for analogue input circuits and for the MICBIAS

generators. CP2 and LDO2 are enabled using the CP2_ENA register bit.

The 32kHz clock must be configured and enabled when using CP2. See “Clocking and Sample Rates” for details of the

system clocks.

When CP2 and LDO2 are enabled, the MICVDD voltage can be selected using the LDO2_VSEL control field. Note that,

when one or more of the MICBIAS generators is operating in normal (regulator) mode, then the MICVDD voltage must be

at least 200mV greater than the highest selected MICBIASn output voltage(s).

When CP2 and LDO2 are enabled, an internal bypass path may be selected, connecting the MICVDD pin directly to the

CPVDD supply. This path is controlled using the CP2_BYPASS register. Note that the bypass path is only supported when

CP2 is enabled.

When CP2 is disabled, the CP2VOUT pin can be configured to be floating or to be actively discharged. This is selected

using the CP2_DISCH register bit.

When LDO2 is disabled, the MICVDD pin can be configured to be floating or to be actively discharged. This is selected using

the LDO2_DISCH register bit.

The MICVDD pin is connected to the output of LDO2. Note that the MICVDD does not support direct connection to an

external supply; MICVDD is always powered internally to the CS47L85.

The Charge Pumps and LDO2 Regulator circuits are illustrated in Figure 86. The associated register control bits are

descrbed in Table 129.

Note that decoupling capacitors and flyback capacitors are required for these circuits. Refer to the “Applications Information”

section for recommended external components.

MICROPHONE BIAS (MICBIAS) CONTROL

There are four MICBIAS generators which provide low noise reference voltages suitable for biasing electret condenser (ECM)

type microphones or powering digital microphones. Refer to the

“Applications Information” section for recommended external

components.

The MICBIAS generators are powered from MICVDD, which is generated by an internal Charge Pump and LDO, as

illustrated in Figure 86.

The MICBIAS outputs can be independently enabled using the MICBn_ENA register bits (where n = 1, 2 3 or 4 for MICBIAS1,

2, 3 or 4 respectively).

When a MICBIAS output is disabled, the output pin can be configured to be floating or to be actively discharged. This is

selected using the MICBn_DISCH register bits.

The MICBIAS generators can each operate as a voltage regulator or in bypass mode. The applicable mode is selected using

the MICBn_BYPASS registers.

In Regulator mode (MICBn_BYPASS=0), the output voltage is selected using the MICBn_LVL register bits. In this mode,

MICVDD must be at least 200mV greater than the required MICBIAS output voltages. The MICBIAS outputs are powered

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