Design details

UM0581

12/26

Doc ID 14961 Rev 1

3.2.1

Onboard power supply

The L4960 is a monolithic power switching regulator delivering 2.5 A at a voltage varying

from 5 V to 40 V in step-down configuration. This is used to provide the 12 V output required

for the external HDD.

The L4978 is a step-down monolithic power switching regulator delivering 2 A at a voltage

between 3.3 V and 50 V. This is used to provide the 5 V output required for the external

HDD.

To power on the microcontroller 1.8 V and 3.3 V power supplies are also provided. The

LD1117A is a low drop voltage regulator able to provide up to 1 A of output current, used for

the 3.3 V STR91xF I/O power supply. The LDS3985 is a low drop voltage regulator. Low

quiescent current and low noise make it suitable for low power applications and is used for

the 1.8 V STR91xF CPU core power supply.

3.3

Microcontroller

The STR912FW44X6 ARM core-based ARM966E-S in a 128-pin LQFP package is the

heart of the STR912FAW44 parallel interface to hard disk demonstration board. For this

microcontroller two power supplies are required: 1.8 V +/- 10% (for the core) and 2.7 to

3.6 V (for the IO).

The microcontroller offers an external memory bus for connecting external parallel

peripherals and memories. The EMI bus resides on ports 7, 8, and 9 and operates with

15 V DC power (this

should meet the

hard disk current

requirements)

Connect the 15 V DC power adapter to J7 or J3. Jumper settings are as follows:

– J7 or J3: 15 V DC adapter is inserted

– J4: connect the jumper between pin 1 and 2

– J5: open (not used)

– J8: connect the jumper between pin 1 and 2

– J9: connect the jumper between pin 2 and pin 3

– J6: power on the external hard disk by connecting the hard disk power-on connector

between J6 and the hard disk

D9 LED

The LED glows when the system gets 5 V power supply

Table 1.

Setting up of power supply (continued)

Power supply

Description