AN-6047

APPLICATION NOTE

© 2006 Fairchild Semiconductor Corporation

www.fairchildsemi.com

Rev. 1.0.3 • 8/22/07

2

System Implementation

The combination of the reset and standby pins offer the system

designer versatility.

In a mobile phone with a clam shell form factor, the reset pins

can be pulled LOW every time the flip is closed. This allows a

full reset of the registers and parallel outputs when the flip is

opened. The standby pin can be pulled LOW to save power

between writes to the display. This allows the micro serializer /

deserializer (µSerDes) to be in a power-down state and keep

the last-known states of the registers and parallel outputs.

These two pins allow the µSerDes pair and the system to

operate efficiently, depending on the systems status. For

example, a typical phone call may consist of:

Opening the flip

Dialing a number

Making the call

Hanging up and closing the flip

During each one of these states, the µSerDes pair can be

enabled and disabled to save the maximum amount of power

(please see Figure 2).

Per Figure 2, the reset and standby (STBY) status during the

phone call would be:

Flip Closed, Reset = L, STBY = L

Open Flip, Reset = H, STBY = H

Dialing Number, Reset = H, STBY = H

Making Call, Reset = H, STBY = L

Closing Flip, Reset = L, STBY = L

Figure 2 – Power Consumed During a Call

When powering on the µSerDes pair, it is recommended that

the standby pin is delayed by 20µs to the reset pin

transitioning HIGH (see Figure 3). Although this delay is not

required for full functionality, it is recommended to ensure that

the deserializer’s reset pin is fully HIGH and the device is

ready to be enabled by the LOW pulse on the CTL lines. If the

deserializer’s power is still transitioning when the CTL lines

transition LOW, the deserializer does not enable.

Figure 3 – Power-up Sequencing