Datasheet

TURBOTRANS
TurboTrans™ Technology
TurboTrans™ Selection
PTH04T230W , PTH04T231W
www.ti.com ............................................................................................................................................. SLTS271C – SEPTEMBER 2006 – REVISED MARCH 2009
TurboTrans technology is a feature introduced in the T2 generation of the PTH/PTV family of power modules.
TurboTrans optimizes the transient response of the regulator with added external capacitance using a single
external resistor. Benefits of this technology include reduced output capacitance, minimized output voltage
deviation following a load transient, and enhanced stability when using ultra-low ESR output capacitors. The
amount of output capacitance required to meet a target output voltage deviation is reduced with TurboTrans
activated. Likewise, for a given amount of output capacitance, with TurboTrans engaged, the amplitude of the
voltage deviation following a load transient is reduced. Applications requiring tight transient voltage tolerances
and minimized capacitor footprint area benefits greatly from this technology.
Using TurboTrans requires connecting a resistor, R
TT
, between the +Sense pin (pin5) and the TurboTrans pin
(pin8). The value of the resistor directly corresponds to the amount of output capacitance required. All T2
products require a minimum value of output capacitance whether or not TurboTrans is used. For the
PTH04T230W, the minimum required capacitance is 200 µ F ceramic. When using TurboTrans, capacitors with a
capacitance × ESR product below 10,000 µ F × m Ω are required. (Multiply the capacitance (in µ F) by the ESR (in
m Ω ) to determine the capacitance × ESR product.) See the Capacitor Selection section of the datasheet for a
variety of capacitors that meet this criteria.
Figure 10 shows the amount of output capacitance required to meet a desired transient voltage deviation with
and without TurboTrans for several capacitor types; TypeA (e.g. ceramic), TypeB (e.g. polymer-tantalum), and
TypeC (e.g. OS-CON). To calculate the proper value of R
TT
, first determine the required transient voltage
deviation limits and magnitude of the transient load step. Next, determine what type of output capacitors is used.
(If more than one type of output capacitor is used, select the capacitor type that makes up the majority of the
total output capacitance). Knowing this information, use the chart in Figure 10 that corresponds to the capacitor
type selected. To use the chart, begin by dividing the maximum voltage deviation limit (in mV) by the magnitude
of the load step (in Amps). This gives a mV/A value. Find this value on the Y-axis of the appropriate chart. Read
across the graph to the 'With TurboTrans' plot. From this point, read down to the X-axis which lists the minimum
required capacitance, C
O
, to meet that transient voltage deviation. The required R
TT
resistor value can then be
calculated using the equation or selected from the TurboTrans table. The TurboTrans tables include both the
required output capacitance and the corresponding R
TT
values to meet several values of transient voltage
deviation for 25%(1.5A), 50%(3A), and 75%(4.5A) output load steps.
The chart can also be used to determine the achievable transient voltage deviation for a given amount of output
capacitance. Selecting the amount of output capacitance along the X-axis, reading up to the 'With TurboTrans'
curve, and then over to the Y-axis, gives the transient voltage deviation limit for that value of output capacitance.
The required R
TT
resistor value can be calculated using the equation or selected from the TurboTrans table.
As an example, consider a 5-V application requiring a 45mV deviation during a 3-A, 50% load transient. A
majority of 330 µ F, 10m Ω ouput capacitors are used. Use the Type B capacitor chart, Figure 11 . Dividing 45mV
by 3A gives 15mV/A transient voltage deviation per amp of transient load step. Select 15mV/A on the Y-axis and
read across to the 'With TurboTrans' plot. Following this point down to the X-axis gives us a minimum required
output capacitance of approximately 820 µ F. The required R
TT
resistor value for 820 µ F can then be calculated or
selected from Table 5 . The required R
TT
resistor is approximately 6.19k Ω .
To see the benefit of TurboTrans, follow the 15mV/A marking across to the 'Without TurboTrans' plot. Following
that point down shows that you would need a minimum of 2700 µ F of output capacitance to meet the same
transient deviation limit. This is the benefit of TurboTrans. A typical TurboTrans schematic is shown in Figure 16 .
Copyright © 2006 – 2009, Texas Instruments Incorporated Submit Documentation Feedback 17
Product Folder Link(s): PTH04T230W PTH04T231W