ipm6220 Intersil Corporation, ipm6220 Datasheet - Page 11
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ipm6220
Manufacturer Part Number
ipm6220
Description
Advanced Triple Pwm And Dual Linear Power Controller For Portable
Manufacturer
Intersil Corporation
Datasheet
1.IPM6220.pdf
(14 pages)
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determined by the ESR (Equivalent Series Resistance) and
voltage rating requirements as well as actual capacitance
requirements. The output voltage ripple is due to the
inductor ripple current and the ESR of the output capacitors
as defined by:
where, 'I
High frequency decoupling capacitors should be placed as
close to the power pins of the load as physically possible. Be
careful not to add inductance in the circuit board wiring that
could cancel the usefulness of these low inductance
components. Consult with the manufacturer of the load
circuitry for specific decoupling requirements.
Use only specialized low-ESR capacitors intended for
switching-regulator applications, at 300kHz, for the bulk
capacitors. In most cases, multiple electrolytic capacitors of
small case size perform better than a single large case
capacitor.
The stability requirement on the selection of the output
capacitor is that the ‘ESR zero’, f
30kHz. This range is set by an internal, single compensation
zero at 6kHz. The ESR zero can be a factor of five on either
side of the internal zero and still contribute to increased
phase margin of the control loop. Therefore:
In conclusion, the output capacitors must meet three criteria: By
varying the values of the soft-start capacitors, it is possible to
provide sequencing of the main outputs at start-up.
3.3V ALWAYS and 5V ALWAYS Output Capacitors
The output capacitors for the linear regulators insure stability
and provide dynamic load current. The 3.3V ALWAYS and
the 5V ALWAYS linear regulators should have, as a
minimum, 10PF capacitors on their outputs.
3.3V Main and 5V Main PWM Output Inductor
Selection
The PWM converters require output inductors. The output
inductor is selected to meet the output voltage ripple
requirements. The inductor value determines the converter’s
ripple current and the ripple voltage is a function of the ripple
current and output capacitor(s) ESR. The ripple voltage
C
V
1. They must have sufficient bulk capacitance to sustain the
2. The ESR must be sufficiently low to meet the desired
3. The ESR zero should be placed, in a rather large range,
OUT
RIPPLE
output voltage during a load transient while the output
inductor current is slewing to the value of the load
transient
output voltage ripple due to the output inductor current,
and
to provide additional phase margin.
=
-------------------------------------------
2
L
=
u
is calculated in the Inductor Selection section.
'I L
S
u
ESR
1
u
ESR
u
f
Z
11
Z
, be between 1.2kHz and
IPM6220
expression is given in the capacitor selection section and the
ripple current is approximated by the following equation:
Input Capacitor Selection
The important parameters for the bulk input capacitor(s) are
the voltage rating and the RMS current rating. For reliable
operation, select bulk input capacitors with voltage and
current ratings above the maximum input voltage and largest
RMS current required by the circuit. The capacitor voltage
rating should be at least 1.25 times greater than the
maximum input voltage and 1.5 times is a conservative
guideline.
The AC RMS input current varies with load as shown in
Figure 9. Depending on the specifics of the input power and
it’s impedance, most (or all) of this current is supplied by the
input capacitor(s). Figure 9 also shows the advantage of
having the PWM converters operating out of phase. If the
converters were operating in phase, the combined RMS
current would be the algebraic sum, which is a much larger
value as shown. The combined out-of-phase current is the
square root of the sum of the square of the individual
reflected currents and is significantly less than the combined
in-phase current.
Use a mix of input bypass capacitors to control the voltage
ripple across the MOSFETs. Use ceramic capacitors for the
high frequency decoupling and bulk capacitors to supply the
RMS current. Small ceramic capacitors can be placed very
close to the upper MOSFET to suppress the voltage induced
in the parasitic circuit impedances.
For board designs that allow through-hole components, the
Sanyo OS-CON® series offer low ESR and good
temperature performance.
For surface mount designs, solid tantalum capacitors can be
used, but caution must be exercised with regard to the
capacitor surge current rating. These capacitors must be
capable of handling the surge-current at power-up. The TPS
series available from AVX is surge current tested.
'I L
4.5
3.5
2.5
1.5
0.5
=
5
4
3
2
1
0
0
OS-CON® is a registered trademark of Sanyo Electric Company, Ltd. (Japan)
V
------------------------------- -
IN
F
FIGURE 9. INPUT RMS CURRENT vs LOAD
–
S
OUT OF PHASE
V
u
OUT
L
1
u
V
--------------- -
3.3V AND 5V LOAD CURRENT
V
OUT
IN
IN PHASE
2
3
3.3V
4
5V
5