33702 Datasheet, PDF (20/24 Pages) Motorola, Inc – 3.0 A Switch-Mode Power Supply with Linear Regulator

Freescale Semiconductor, Inc.
Table 5. Command Byte Definitions
Operation
Address
Value
Action
Voltage Margining 0 0 1 0 0 0 0 0 1st Command
(As a 2nd
Command Byte)
0 0 1 x 0 0 0 0 Output Normal
001x0001
+ 1%
001x0010
+ 2%
001x0011
+ 3%
001x0100
+ 4%
LDO Output: x=0 0 0 1 x 0 1 0 1
+ 5%
Switcher Output x=1 0 0 1 x 0 1 1 0
+ 6%
001x0111
+ 7%
001x1001
- 1%
001x1010
- 2%
001x1011
- 3%
001x1100
- 4%
001x1101
- 5%
001x1110
- 6%
001x1111
- 7%
Watchdog
Programming
(As a 2nd
Command Byte)
0 1 1 0 0 0 0 0 1st Command
01100000
WD OFF
(Note 13)
0 1 1 0 1 0 0 0 WD 1280 ms
WinOFF
0 1 1 0 1 0 0 1 WD 320 ms
WinOFF
0 1 1 0 1 0 1 0 WD 80 ms
WinOFF
0 1 1 0 1 0 1 1 WD 20 ms
WinOFF
0 1 1 0 1 1 0 0 WD 1280 ms
WinON
0 1 1 0 1 1 0 1 WD 320 ms
WinON
0 1 1 0 1 1 1 0 WD 80 ms
WinON
0 1 1 0 1 1 1 1 WD 20 ms
WinON
Notes
13. The Watchdog feature will be turned ON automatically
after receiving any other valid command byte changing
watchdog time.
Security in Writing Commands
All writing operations are critical and must not be
inadvertently latched after a false command. To improve the
security level, a so-called first command is defined to initiate
each write communications.
A first command has the Command Byte address field equal
to the related operation one, followed by a null value field (all
zeros). Table 6 summarizes first command definitions. The
master sends the first command before the Command Byte for
the intended operation.
Table 6. First Command Definitions
First Command
Operation
001 00000
Voltage Margining
011 00000
Watchdog Programming
Voltage Margining Operation
After starting the communication in Writing mode, the master
sends the first command followed by the specific Command
Byte to set the required voltage margining for either the LDO or
the switcher (see Figure 17). To achieve a simultaneous set for
both LDO and switcher, two specific commands must be issued
in sequence after the first command, one for each supply.
0 0 1 0 0 0 0 0 Ack 0 0 1 x x x x x
First Byte for Voltage Margining
Command Byte
Figure 17. Voltage Margining Programming
(One Supply Only)
Note x bits are defined in Table 5.
Watchdog Programming Operation
For watchdog operation control, the master periodically
sends a watchdog first command followed by a command byte
selecting, or confirming, the watchdog period according to the
options listed in Table 5. Also see Figure 18.
The internal watchdog timer will be cleared each time a
watchdog command is written into the device, provided it
arrives during the window open time. The Command 01100000
sent twice will shut the time OFF, and the watchdog function will
be disabled. Any other valid watchdog command turns on the
timer again.
0 1 1 0 0 0 0 0 Ack 0 1 1 x x x x x
First Byte for Watchdog Programming
Command Byte
Figure 18. Watchdog Timer Programming
Note x bits are defined in Table 5.
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