CS47L85 datasheet(356/370 Pages) CIRRUS

356 / 370 page

CS47L85

356

Rev 4.3

CHARGE PUMP COMPONENTS

The CS47L85 incorporates two Charge Pump circuits, identified as CP1 and CP2.

CP1 generates the CP1VOUTP and CP1VOUTN supply rails for the ground-referenced headphone drivers; CP2 generates

the CP2VOUT supply rail for the microphone bias (MICBIAS) regulators.

Decoupling capacitors are required on each of the Charge Pump outputs. Two fly-back capacitors are required for CP1; a

single fly-back capacitor is required for CP2.

The recommended Charge Pump capacitors for CS47L85 are detailed below in Table 137.

DESCRIPTION

CAPACITOR

CP1VOUT1P decoupling

Required capacitance is 2.0

F at 2V.

Suitable component typically 4.7

F.

CP1VOUT1N decoupling

Required capacitance is 2.0

F at 2V.

Suitable component typically 4.7

F.

CP1 fly-back 1

(connect between CP1C1A and CP1C1B)

Required capacitance is 1.0

F at 2V.

Suitable component typically 2.2

F.

CP1VOUT2P decoupling

Required capacitance is 2.0

F at 2V.

Suitable component typically 4.7

F.

CP1VOUT2N decoupling

Required capacitance is 2.0

F at 2V.

Suitable component typically 4.7

F.

CP1 fly-back 2

(connect between CP1C2A and CP1C2B)

Required capacitance is 1.0

F at 2V.

Suitable component typically 2.2

F.

CP2VOUT decoupling

Required capacitance is 1.0

F at 3.6V.

Suitable component typically 4.7

F.

CP2 fly-back

(connect between CP2CA and CP2CB)

Required capacitance is 220nF at 2V.

Suitable component typically 470nF.

Table 137 Charge Pump External Capacitors

Ceramic capacitors are recommended for these Charge Pump requirements. Note that, due to the wide tolerance of many

types of ceramic capacitors, care must be taken to ensure that the selected components provide the required capacitance

across the required temperature and voltage ranges in the intended application. Ceramic capacitors with X5R dielectric are

recommended.

The positioning of the Charge Pump capacitors is important, particularly the fly-back capacitors. These capacitors should

be placed as close as possible to the CS47L85. The component choice and positioning of the CP1 components are more

critical than those of CP2, due to the higher output power requirements of CP1.

EXTERNAL ACCESSORY DETECTION COMPONENTS

The external accessory detection circuit measures jack insertion using the JACKDET1 and JACKDET2 pins. The insertion

switch status is detected using an internal pull-up resistor circuit on the respective pin. The logic thresholds associated with

the each of the JACKDETn pins are the same, as noted in the “Electrical Characteristics” section. Note that an external

resistor (e.g., 500k

) can be used to lower the effective jack detection thresholds; this provides support for different jack

switch configurations.

Microphone detection and key-button press detection is supported using the MICDETn pins. The applicable pin should be

connected to one of the MICBIASn outputs, via a 2.2k

 bias resistor, as described in the “Microphone Bias Circuit” section.

Note that, when using the External Accessory Detection function, the MICBIASn resistor must be 2.2k

 +/-2%.

A recommended circuit configuration, including headphone output on HPOUT1 and microphone connections, is shown in

Figure 97

. See “Analogue Input Paths” for details of the DC-blocking microphone input capacitor selection.

The recommended external components and connections for microphone / push-button detection are illustrated in Figure

98.

Note that, when using the Microphone Detect circuit, it is recommended to use the IN1B or IN2B analogue microphone input

paths, to ensure best immunity to electrical transients arising from the external accessory.

CS47L85 Datasheet(PDF) 356 Page - Cirrus Logic

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