User's Manual

LTE Module

EC20 Hardware Design

EC20_Hardware_Design Confidential / Released 42 / 83

The following figure shows the reference design of PCM interface with external codec IC.

PCM_IN

PCM_OUT

PCM_SYNC

PCM_CLK

I2C_SCL

I2C_SDA

Module

1.8V

4.7K

BCLK

LRCK

DAC

ADC

SCL

SDA

BIAS

MICBIAS

INP

INN

LOUTP

LOUTN

ALC5616

Figure 24: Reference Circuit of PCM Application with Audio Codec

1. It is recommended to reserved RC (R=22ohm, C=22pF) circuit on the PCM lines, especially for

PCM_CLK.

2. EC20 works as a master device pertaining to I2C interface.

3.13. ADC Function

The module provides two analog-to-digital converters (ADC) to digitize the analog signal to 15-bit digital

data such as battery voltage, temperature and so on. Using AT command AT+QADC=0 can read the

voltage value on ADC0 pin. Using AT command AT+QADC=1 can read the voltage value on ADC1 pin.

For more details of these AT commands, please refer to document [2].

In order to improve the accuracy of ADC, the trace of ADC should be surrounded by ground.

Table 15: Pin Definition of the ADC

Pin Name

Pin No.

Description

ADC0

General purpose analog to digital converter

ADC1

General purpose analog to digital converter

NOTES