TPS7H5005-SEP, TPS7H5006-SEP, TPS7H5007-SEP, TPS7H5008-SEP
SLVSGG1 – FEBRUARY 2022
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CHICC × 0.6 V
tdelay
tdelay
tHICC
tHICC
=
=
=
=
80 A
(75)
(76)
(77)
(78)
3.3 nF × 0.6 V
80 A
= 24.75 s
CHICC × (1 V 0.3 V)
1 A
3.3 nF × (1 V 0.3 V)
1 A
= 2.31 ms
Note that as mentioned in Section 8.3.15, the delay time calculation is an approximation and the actual time
depends on the nature of the overcurrent.
9.2.2.14 Frequency Compensation Components
For this design, Type 2A compensation was used. With a target crossover frequency of 10 kHz, the guidelines
shown in Section 8.3.18 are used here to determine the compensation values needed for the compensation
network. The power stage transconductance is first needed in order to calculate the frequency compensation
component values.
NP × NCSS
gmPS
=
CCSR × RCS × NS × NCSP
(79)
(80)
2.5 × 100
A
V
gmPS
=
= 16.2
2.06 × 7.5 × 1 × 1
With the power stage transconductance calculated as 16.2 A/V, the values of the external components needed
at the COMP pin can be resolved.
2 × fc × VOUT × COUT
RCOMP
=
gmea × VREF × gmPS
(81)
2 × 10 kHz × 5 V × 2.3 mF
6 A
RCOMP
=
= 40.4 kΩ
A
V
1800 × 10
× 0.613 V × 16.2
V
(82)
(83)
(84)
VOUT × COUT
IOUT × RCOMP
CCOMP
=
5 V × 2.3 mF
20 A × 40.2 k
CCOMP
=
= 14.3 nF
For the output capacitance 7 × 330-μF polymer tantalum capacitors were used to meet the 2.3-mF value that
was needed for the design. At the selected switching frequency and output voltage, each of these capacitors had
an ESR of roughly 6 mΩ. As such, the equivalent ESR used to determine the frequency of the ESR zero in the
frequency response is equivalent the parallel resistance of these seven capacitors, which is 0.86 mΩ. The ESR
zero frequency is then used in the calculation of CHF
.
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56
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