34701_07 Datasheet, PDF (28/38 Pages) Freescale Semiconductor, Inc – 1.5 A Switch-Mode Power Supply with Linear Regulator

FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
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 24. Voltage Margining Programming
(One Supply Only)
Note: x bits, which set the voltage margining value are
defined in Table 8.
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 8. See Figure 25 for the
watchdog timer programming command example.
The internal watchdog timer is turned ON by receiving a
valid Watchdog Programming command (after receiving the
Watchdog Programming First Command), and it is cleared
each time the next Watchdog Programming command is
written into the device, provided it arrives during the window
open time. Thus, the Watchdog Programming command
clears the timer and sets the new timing conditions at the
same time. The Watchdog Programming First Command
01100000 sent twice shuts the timer OFF, and the watchdog
function is disabled. Any other valid watchdog command
turns the timer ON 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 25. Watchdog Timer Programming
Note: x bits, which set the watchdog timer value are
defined in Table 8, page 27.
Communication Stop
Only the master can terminate the data transfer by issuing
a STOP condition. The slave waits for this condition to
resume its initial state waiting for the next START condition
(see Figure 26).
COMPLETE DATA TRANSFER EXAMPLES
The master device controlling the I²C bus always starts
addressing a 34701 slave IC in writing mode (R/W = 0) to
enable it to write a Command Byte just after receiving the
address acknowledge sent by 34702. I²C bus protocol
defines this circumstance as a master-transmitter and slave-
receiver configuration.
Figure 27 illustrates a communication beginning with the
slave address, the first command for voltage margining, and
a third byte containing the address field 001 and the value
field 00101 corresponding with the LDO fifth setting (LDO
output voltage = +5% above its nominal value). If a
simultaneous setting for switcher is needed, a fourth byte
should be included before the STOP condition (P); for
instance, 001 11100 to set the switcher in its twelfth setting
(switcher output voltage = -5% below its nominal value) - see
Figure 28.
The example of data transfer setting the Watchdog timer is
shown in the Figure 26.
S A6 A5 A4 A3 A2 A1 A0 0 Ack
START
Slave Address
Write
0 1 1 0 0 0 0 0 Ack
First Command for Watchdog Programming
0 1 1 0 1 0 0 1 Ack P
Address Field Value Field:
STOP
Time-out WD = 320 ms
(Window OFF)
Figure 26. Data Transfer Example - Watch Dog Timer
Setting.
S A6 A5 A4 A3 A2 A1 A0 0 Ack
START
Slave Address
Write
0 0 1 0 0 0 0 0 Ack
First Command for Voltage Margining
0 0 1 0 0 1 0 1 Ack P
Address Field Value Field = LDO
5th Setting
STOP
Figure 27. Data Transfer Example - LDO Voltage
Margining
34701
28
Analog Integrated Circuit Device Data
Freescale Semiconductor