Texas Instruments TPS61085 Evaluation Module TPS61085EVM-355 TPS61085EVM-355 Datenbogen
Produktcode
TPS61085EVM-355
IN
S
125 × V
× V × Cout
R3 =
L × Iout_max
S
V × Cout
C5 =
5 × Iout_max × R3
www.ti.com
Setup and Test Results
2.2
EVM Operation
First there should be jumpers connected to JP1 and JP2, to make sure that the part gets the proper
signals on the EN and FREQ pins. The user has to connect an input power supply set between 2.3 V and
6 V between headers J1 and J3 in order for the EVM to operate. The absolute maximum input voltage is
7 V. The user can connect a load resistance between J4 and J6. Connect a jumper between pins 1 and 2
of JP1 to enable the device.
signals on the EN and FREQ pins. The user has to connect an input power supply set between 2.3 V and
6 V between headers J1 and J3 in order for the EVM to operate. The absolute maximum input voltage is
7 V. The user can connect a load resistance between J4 and J6. Connect a jumper between pins 1 and 2
of JP1 to enable the device.
2.3
Compensation (R3, C5)
The regulator loop can be compensated by adjusting the external components connected to the COMP
pin. The COMP pin is the output of the internal transconductance error amplifier. Standard values of
R3 = 13 k
pin. The COMP pin is the output of the internal transconductance error amplifier. Standard values of
R3 = 13 k
Ω
and C5 = 3.3 nF will work for the majority of the applications.
Please refer to
for dedicated compensation networks giving an improved load transient response.
The following equations can be used to calculate R3 and C5:
(1)
Table 2. Recommended Compensation Network Values at High/Low Frequency
FREQUENCY
L (
m
H)
V
S
(V)
V
IN
± 20% (V)
R3(k
Ω
)
C5
5
82
1.1 nF
15
3.3
75
1.6 nF
5
51
1.1 nF
High (1.2 MHz)
3.3
12
3.3
47
1.6 nF
5
30
1.1 nF
9
3.3
27
1.6 nF
5
43
2.2 nF
15
3.3
39
3.3 nF
5
27
2.2 nF
Low (650 kHz)
6.8
12
3.3
24
3.3 nF
5
15
2.2 nF
9
3.3
13
3.3 nF
gives conservatives R3 and C5 values for certain inductors, input and output voltages providing a
very stable system. For a faster response time, a higher R3 value can be used to enlarge the bandwidth,
as well as a slightly lower value of C5 to keep enough phase margin. These adjustments should be
performed in parallel with the load transient response monitoring of TPS61085 to make sure that the
system is still stable.
as well as a slightly lower value of C5 to keep enough phase margin. These adjustments should be
performed in parallel with the load transient response monitoring of TPS61085 to make sure that the
system is still stable.
3
SLVU265A – August 2008 – Revised October 2010
TPS61085EVM
Copyright © 2008–2010, Texas Instruments Incorporated