8.2 Typical Application

The CDC3RL02 is designed for use in mobile applications as shown in Figure 8-2. In this example, a single

low noise TCXO system clock source is buffered to drive a mobile GPS receiver and WLAN transceiver. Each

peripheral independently requests an active clock by asserting a single clock request line (CLK_REQ_1 or

CLK_REQ_2). When both clock request lines are inactive, the CDC3RL02 enters a low current shutdown mode.

In this mode, the LDO output, CLK_OUT_1, and CLK_OUT_2 are pulled to GND and the TCXO is not powered.

LDO

TCXO CLK

TCXO REQ

TCXO CLK

TCXO REQ

GPS

WLAN

TCXO

1µF

2.2µF

Li

CLK_REQ_1

CLK_OUT_1

CLK_REQ_2

CLK_OUT_2

GND

VBATT

VLDO

CDC3RL02

MCLK _IN

Copyright © 2017, Texas Instruments Incorporated

Figure 8-2. Mobile Application

When either peripheral requests the clock, the CDC3RL02 enables the LDO and powers the TCXO. The TCXO

output (square wave, sine wave, or clipped sine wave) is converted to a square wave and buffered to the

requested output.

8.2.1 Design Requirements

For the typical application, the user must know the following parameters.

Table 8-1. Design Parameters

PARAMETER

DESCRIPTION

EXAMPLE VALUE

VBATT

Input voltage from battery or power supply

3.7V

MCLK_IN

Input frequency from a TCXO

26MHz

8.2.2 Detailed Design Procedure

The designer must verify that all parameters are within the ranges specified in Recommended Operating

Conditions.

Each device which receives a clock output from the CDC3RL02 must have the CLK request pin connected to

the appropriate CLK_REQ pin on the CDC3RL02. This pin enables the output buffer when a device requests the

clock signal.

Control of the clock outputs is possible by using a GPIO from a controller to control the CLK_REQ pins.

If one of the outputs is unused, then tie the CLK_REQ and CLK_OUT pins to ground. If the user wants a

CLK_OUT pin always enabled, tie the paired CLK_REQ pin to an external 1.8V source (not VLDO because the

LDO output is not enabled until at least one CLK_REQ pin is high).

CDC3RL02

SCHS371H – NOVEMBER 2009 – REVISED OCTOBER 2024

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