Datasheet

PWM −A
1 2 3 4 5 6 7 8 9
EXT CLK−A
EXT CLK−S
1 2 3 4 5 6 7 8 1
11
10
32
PWM −S
UDG−06032
0
50
100
150
200
250
300
350
400
450
100 200 300 400 500 600 700 800 900 1000
RT- Timing Resistor (k
Phase Switching Frequency (kHz)
C001
TPS40140
SLUS660H –SEPTEMBER 2005–REVISED JUNE 2013 www.ti.com
PHASE FREQUENCY
vs
TIMING RESISTOR
Figure 5-6. Phase Switching Frequency vs Timing Resistance
5.21 SYNCHRONIZING A SINGLE CONTROLLER TO AN EXTERNAL CLOCK
The TPS40140 has the ability to synchronize a single controller to an external clock. The clock must be a
pulse stream at 6 or 8 times the master PWM frequency. See Figure 5-7.
Figure 5-7. Synchronizing a Single Controller to an External Clock
Synchronizing the single controller to an external clock is similar to synchronizing a clock slave to a clock
master. The single controller is put in clock slave mode by connecting the RT pin to BP5, disabling the
internal clock generator. If the external CLKIO signal is a clock stream without any missing pulses, the
master synchronize to an arbitrary pulse so there is no determinant phase synchronization. Without a
missing pulse, the PWM frequency is 1/8 of the external clock. If the external CLKIO signal has a missing
pulse every 6 cycles or 8 cycles, the controller synchronizes based on the missing pulse which would be
22 APPLICATION INFORMATION Copyright © 2005–2013, Texas Instruments Incorporated
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