Datasheet

Efficiency
2-8
2.3 Efficiency
The TPS54x80EVM-228 efficiency depends on output voltage, even though
the power losses are roughly the same for any output voltage. Efficiency also
depends on input voltage. For the output current below 3 A, the efficiency is
higher at 3.3-V input voltage because of lower switching losses. For the output
current above 3 A, the efficiency is better at 5-V input voltage because of lower
drain-to-source resistance of integrated FETs driven by higher gate voltage.
The efficiency shown in Figure 2-8 is for 5-V input (TPS54680, TPS54880)
and 3.3-V input (TPS54680) at ambient temperature of 25°C.
Figure 2-8. Measured Efficiency
60
65
70
75
80
85
90
95
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6
V
O
= 1.8 V
V
O
= 1.2 V
V
O
= 0.9 V
V
I
= 3.3 V,
F
(SW)
= 700 kHz
Efficiency - %
TPS54680
EFFICIENCY
vs
OUTPUT CURRENT
I
O
- Output Current - A
50
55
60
65
70
75
80
85
90
95
100
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8
V
I
= 5 V,
F
(SW)
= 700 kHz
Efficiency - %
TPS54680/TPS54880
EFFICIENCY
vs
OUTPUT CURRENT
I
O
- Output Current - A
V
O
= 1.8 V
V
O
= 1.2 V
V
O
= 0.9 V
The input current, consumed by 3.3-V output regulator TPS54x10, is excluded
from these data. The measurements relate only to the core voltage channel
provided by tracking regulators TPS54680 and TPS54880. Efficiency is lower
at higher ambient temperatures, due to temperature variation in the
drain-to-source resistance of the MOSFETs. The efficiency is slightly lower at
700 kHz than at lower switching frequencies, due to the switching losses in the
MOSFETs.