Freescale Semiconductor

6

1.1.2

Thermal Characteristics

Table 3 lists the thermal characteristics.

1.1.3

Power Requirements

To prevent high current conditions due to possible improper sequencing of the power supplies, use an external Schottky diode

as shown in Figure 3, connected between the DSP56724/DSP56725 IO_VDD and Core_VDD power pins.

Figure 3. Prevent High Current Conditions by Using External Schottky Diode

If an external Schottky diode is not used (to prevent a high current condition at power-up), then IO_VDD must be applied ahead

of Core_VDD, as shown in Figure 4.

Figure 4. Prevent High Current Conditions by Applying IO_VDD Before Core_VDD

Table 3. Thermal Characteristics

Characteristic

Symbol

LQFP Values

Unit

Natural Convection, Junction-to-ambient thermal

Single layer board

(1s)

57 for 80 QFP

49 for 144 QFP

Four layer board

(2s2p)

44 for 80 QFP

40 for 144 QFP

10 for 80 QFP

9 for 144 QFP

Note:

1. Junction temperature is a function of die size, on-chip power dissipation, package thermal resistance, mounting site (board)

temperature, ambient temperature, air flow, power dissipation of other components on the board, and board thermal

resistance.

2. Per SEMI G38-87 and JEDEC JESD51-2 with the single layer board horizontal.

3. Thermal resistance between the die and the case top surface as measured by the cold plate method

(MIL SPEC-883 Method 1012.1).

IO_VDD

Core_VDD

External

Schottky

Diode

Core_VDD

IO_VDD