DSP56852E/D View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

DSP56852E/D

16-bit Digital Signal Processor

Motorola => Freescale 

Freescale Semiconductor, Inc.

Supply Voltage Sequencing and Separation Cautions

VDD should not be allowed to rise early (1). This is usually avoided by running the regulator for the VDD

supply (1.8V) from the voltage generated by the 3.3V VDDIO supply, see Figure 5. This keeps VDD from

rising faster than VDDIO.

VDD should not rise so late that a large voltage difference is allowed between the two supplies (2). Typically

this situation is avoided by using external discrete diodes in series between supplies, as shown in Figure 5.

The series diodes forward bias when the difference between VDDIO and VDD reaches approximately 2.1,

causing VDD to rise as VDDIO ramps up. When the VDD regulator begins proper operation, the difference

between supplies will typically be 0.8V and conduction through the diode chain reduces to essentially

leakage current. During supply sequencing, the following general relationship should be adhered to:

VDDIO > VDD > (VDDIO - 2.1V)

In practice, VDDA is typically connected directly to VDDIO with some filtering.

3.3V

Supply Regulator

VDDIO, VDDA

1.8V

VDD

Regulator

Figure 5. Example Circuit to Control Supply Sequencing

DSP56852 Technical Data

17

Preliminary

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