Datasheet

Modifications
1-4
Table 1−4.TPS54972EVM-222 Performance Specification Summary
Specification Test Conditions Min Typ Max Units
Input voltage range 3.0 3.3 4.0 V
Output voltage set point 0.42 1.25 1.75 V
Output current range V
I
= 3 V to 4 V −9 9 A
Line regulation I
O
= 4.5 A 0.4 mV
Load regulation V
I
= 5 V, I
O
= 0 A to 9 A 8.0 mV
I
O
= 2.25 A to 6.75 A, t
r
= 40 µs
−35 mV
PK
Load transient response
I
O
= 2.25 A to 6.75 A, t
r
= 40
µ
s
75 µs
Load transient response
I
O
= 6.75 A to 2.25 A, t
f
= 40 µs
40 mV
PK
I
O
= 6.75 A to 2.25 A, t
f
= 40
µ
s
75 µs
Loop bandwidth V
I
= 3 V 71 kHz
Phase margin V
I
= 3 V 41 °
Loop bandwidth V
I
= 3.6 V 80 kHz
Phase margin V
I
= 3.6 V 42 °
Input ripple voltage 340 400 mV
PP
Output ripple voltage 7 10 mV
PP
Output rise time 4.7 8.4 15 ms
Operating frequency 700 kHz
Maximum efficiency V
I
= 3.3 V, Vo = 1.25 V, I
O
= 2.5 A 89.7%
1.3 Modifications
The TPS54x72EVM−222 is designed to demonstrate the small size that can
be attained when designing with the TPS54x72, so many of the features which
allow for extensive modifications have been ommited from this EVM.
Changing the V
(DDQ)
voltage from 0.92 V to 3.5 V can change the output
voltage in the range of 0.46 V to 1.75 V. Output voltages above 1.75 V can be
obtained by modifying the REFIN voltage divider of R6 and R7, and scaling the
output feedback voltage into the VSENSE pin using the voltage divider of R1
and R9 (normally not used). To maintain the output-tracking rate of one half
the V
(DDQ)
input, the R6/R7 divider should scale V
(DDQ)
by a factor of four and
R1/R9 divder should scale V
(TTQ)
by a factor of two. To accomplish this,
replace R6 with a 30.1 kΩ resistor and add R9 as a 10 kΩ resistor. The
minimum output voltage is limited by the minimum controllable ontime of the
device, 200 ns, and is dependent upon the duty cycle and operating frequency.
The approximat minimum output voltage can be calculated using :
V
OUTMIN
+ 200 ns f
s
V
INMIN
The switching frequency may be trimmed to any value between 280 kHz and
700 kHz by changing the value of R5. Decreasing the switching frequency
results in increased output ripple unless the value of L1 is increased. A plot of
the value of RT versus the switching frequency is given in Figure 1−1.
(1)