Datasheet
Smart Sync
GND
PTH08T250W
Track
C
I1
+
UDG-08149
V
I
Sync
TurboTrans
+Sense
V
O
-Sense
+
GND
C
O1
PRE
GND
Q
Q
CLK
CLK
D
V
CC
GND
PTH08T240W
Track
C
I2
+
V
I
Sync
TurboTrans
+Sense
R
SET2
V
O
Adj
V
O
-Sense
+
GND
C
O2
0°
180°
V
O2
f
CLK
= 2 x f
MOD
SN74LVC2G74
V
I
= 5 V
V
O1
R
SET1
V
O
Adj
AGND
PTH08T255W
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........................................................................................................................................................................................... SLTS290 – NOVEMBER 2008
The overtemperature protection is a last resort mechanism to prevent thermal stress to the regulator.
Operation at or close to the thermal shutdown temperature is not recommended and reduces the long-term
reliability of the module. Always operate the regulator within the specified safe operating area (SOA) limits for
the worst-case conditions of ambient temperature and airflow.
Smart Sync is a feature that allows multiple power modules to be synchronized to a common frequency. When
not used, this pin must be connect to GND. Driving the Smart Sync pins with an external oscillator set to the
desired frequency, synchronizes all connected modules to the selected frequency. The synchronization
frequency can be higher or lower than the nominal switching frequency of the modules within the range of
240 kHz to 400 kHz.
Synchronizing modules powered from the same bus eliminates beat frequencies reflected back to the input
supply, and also reduces EMI filtering requirements. Eliminating the low beat frequencies (usually < 10kHz) allows
the EMI filter to be designed to attenuate only the synchronization frequency. Power modules can also be
synchronized out of phase to minimize ripple current and reduce input capacitance requirements.
The PTH08T255W requires that the external synchronization frequency be present before a valid input voltage is
present or before release of the inhibit control.
Figure 14 shows a typical circuit with two modules synchronized 180 ° out of phase using a D flip-flop.
Figure 14. Typical Smart Sync Schematic
Copyright © 2008, Texas Instruments Incorporated 19
Product Folder Link(s): PTH08T255W