34701_07 Datasheet, PDF (27/38 Pages) Freescale Semiconductor, Inc – 1.5 A Switch-Mode Power Supply with Linear Regulator

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
DATA Definition
The DATA field in the single Data Transfer contains one or
several Command Bytes. The Command Byte identifies the
kind of operation required by the master to be performed and
has two fields, as illustrated in Figure 23:
1. Address field
2. Value field
The address field is selected from the list in Table 7.
MSB
Bits
LSB
76 543 21 0
D7 D6 D5 D4 D3 D2 D1 D0
Address Field Value Field
Figure 23. Command Byte
Table 7. Address Field Definitions
Address Field
Operation
001
Voltage Margining
011
Watchdog
Write
W
W
Refer to Table 8, page 27, which summarizes the value
field definitions for the entire set of operation options.
Table 8. Command Byte Definitions
Operation
Address
Value
Action
Voltage Margining 0 0 1 0 0 0 0 0 1st Command
(As a 2nd
001x0000
Command Byte)
Output
Nominal
001x0001
+ 1.0%
001x0010
001x0011
+ 2.0%
+ 3.0%
001x0100
+ 4.0%
LDO Output: x=0 0 0 1 x 0 1 0 1
+ 5.0%
Switcher Output
x=1
001x0110
001x0111
001x1000
001x1001
001x1010
001x1011
001x1100
001x1101
001x1110
+ 6.0%
+ 7.0%
- 1.0%
- 2.0%
- 3.0%
- 4.0%
- 5.0%
- 6.0%
- 7.0%
Table 8. Command Byte Definitions
Watchdog
Programming
(As a 2nd
Command Byte)
0 1 1 0 0 0 0 0 1st Command
01100000
WD OFF
(24)
0 1 1 0 1 0 0 0 WD 1280 ms
Wind. OFF
0 1 1 0 1 0 0 1 WD 320 ms
Wind. OFF
0 1 1 0 1 0 1 0 WD 80 ms
Wind. OFF
0 1 1 0 1 0 1 1 WD 20 ms
Wind. OFF
0 1 1 0 1 1 0 0 WD 1280 ms
Wind. ON
0 1 1 0 1 1 0 1 WD 320 ms
Wind. ON
0 1 1 0 1 1 1 0 WD 80 ms
Wind. ON
0 1 1 0 1 1 1 1 WD 20 ms
Wind. ON
Notes
24. The Watchdog timer is turned ON automatically after
receiving any other valid command byte changing watchdog
time.
Security in Writing Commands
To improve the security level, a so-called first command is
defined to initiate each write communications. The first
command identifies the operation, which is executed by the
following Command Byte.
A first command has the address field equal to the related
operation one, followed by a null value field (all zeros).
Table 9 summarizes first command definitions. The master
sends the first command before the Command Byte for the
intended operation.
Table 9. 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 24). 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.
Analog Integrated Circuit Device Data
Freescale Semiconductor
34701
27