Datasheet

CL
f
LC
×
=
p2
1
TPS62130
PVIN
AVIN
EN
SS/TR
DEF
FSW
SW
VOS
PG
FB
AGND
PGND
TPS62130
PVIN
AVIN
EN
SS/TR
DEF
FSW
SW
VOS
PG
FB
AGND
PGND
R1
R2
VOUT1
VOUT2
TPS62130, TPS62130A
TPS62131, TPS62132, TPS62133
www.ti.com SLVSAG7B –NOVEMBER 2011–REVISED JUNE 2013
Once the SS/TR pin voltage reaches about 1.2V, the internal voltage is clamped to the internal feedback voltage
and device goes to normal regulation. This works for rising and falling tracking voltages with the same behavior,
as long as the input voltage is inside the recommended operating conditions. For decreasing SS/TR pin voltage,
the device doesn't sink current from the output. So, the resulting decrease of the output voltage may be slower
than the SS/TR pin voltage if the load is light. When driving the SS/TR pin with an external voltage, do not
exceed the voltage rating of the SS/TR pin which is V
IN
+0.3V.
If the input voltage drops into undervoltage lockout or even down to zero, the output voltage will go to zero,
independent of the tracking voltage. Figure 40 shows how to connect devices to get ratiometric and simultaneous
sequencing by using the tracking function.
spacing
Figure 40. Sequence for Ratiometric and Simultaneous Startup
spacing
The resistive divider of R1 and R2 can be used to change the ramp rate of VOUT2 faster, slower or the same as
VOUT1.
A sequential startup is achieved by connecting the PG pin of VOUT1 to the EN pin of VOUT2. Ratiometric start
up sequence happens if both supplies are sharing the same soft start capacitor. Equation 10 calculates the soft
start time, though the SS/TR current has to be doubled. Details about these and other tracking and sequencing
circuits are found in SLVA470.
Note: If the voltage at the FB pin is below its typical value of 0.8V, the output voltage accuracy may have a wider
tolerance than specified.
Output Filter And Loop Stability
The devices of the TPS6213X family are internally compensated to be stable with L-C filter combinations
corresponding to a corner frequency to be calculated with Equation 12:
(12)
Proven nominal values for inductance and ceramic capacitance are given in Table 1 and are recommended for
use. Different values may work, but care has to be taken on the loop stability which will be affected. More
information including a detailed LC stability matrix can be found in SLVA463.
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Product Folder Links: TPS62130, TPS62130A TPS62131 TPS62132 TPS62133