ipm6220 Intersil Corporation, ipm6220 Datasheet - Page 10

• Manufacturer Part Number: ipm6220
• Description: Advanced Triple Pwm And Dual Linear Power Controller For Portable
• Manufacturer: Intersil Corporation

loop is operating open circuit and the output voltage varies
with the output load resistance, Ro, as given by:
Where Vin is the 5V Main voltage, Dmax = 0.33, L is the
value of the boost inductor, L3, and F = 100kHz. This
provides automatic output current limiting. When the
maximum duty cycle has been reached and for a given
inductor, a further reduction in Ro by one-half will pull the
output voltage down to 0.707 of nominal and cause an
under-voltage condition.
The 12V converter starts to operate at the same time as the
5V Main converter. The rising voltage on the 5V Main output
and the 33% duty cycle limit provides a similar soft-start, as
the 5V Main, for the 12V output.
3V ALWAYS, 5V ALWAYS Linear
Regulators
The 3.3V ALWAYS and 5V ALWAYS outputs are derived
from the battery voltage and are the first voltages available
in the notebook when power on is initiated. The 5V ALWAYS
output is generated directly from the battery voltage by a
linear regulator. It is used to power the system micro-
controller and to internally power the chip and the gate
drivers. The 3.3V ALWAYS output is generated from the 5V
ALWAYS output and may be used to power the keyboard
controller or other peripherals. The combined current
capability of these outputs is 50mA. When the 5V Main
output is greater than it’s undervoltage level, it is switched to
the 5V ALWAYS output via an internal 1.3
switch. Simultaneously, the 5V ALWAYS linear regulator is
disabled to prevent excessive power dissipation.
The rise time of the 5V ALWAYS is determined by the value
of the output capacitance on the 5V and 3.3V ALWAYS
outputs. The internal regulator is current limited to about
180mA, so the start up time is approximately:
Where C
3.3V ALWAYS outputs.
Power Good Status
The IPM6220 monitors all the output voltages except for the
3.3V ALWAYS. A single power-good signal, PGOOD, is
issued when soft-start is completed and all monitored
outputs are within 10% of their respective set points. After
the soft-start sequence is completed, undervoltage
protection latches the chip off when any of the monitored
outputs drop below 75% of its set point.
A ‘soft-crowbar’ function is implemented for an overvoltage
on the 3.3V Main or 5V Main outputs. If the output voltage
goes above 115% of their nominal output level, the upper
t
Vo
=
=
C
Vin
OUT
OUT
u
u
Dmax
-------------------
180mA
5V
is the sum of the capacitances on the 5V and
§
©
------------------ -
2 LxF
Ro
·
¹
10
:
MOSFET
IPM6220
MOSFET is turned off and the lower MOSFET is turned on.
This ‘soft-crowbar’ condition will be maintained until the
output voltage returns to the regulation window and then
normal operation will continue.
This ‘soft-crowbar’ and monitoring of the output, prevents the
output voltage from ringing negative as the inductor current
flows in the ‘reverse’ direction through the lower MOSFET
and output capacitors.
Over-Temperature Protection
The IC incorporates an over-temperature protection circuit
that shuts all the outputs down when the die temperature
exceeds 150
when the die temperature cools to 125
Component Selection Guidelines
Output Capacitor Selection
The output capacitors for each output have unique
requirements. In general, the output capacitors should be
selected to meet the dynamic regulation requirements
including ripple voltage and load transients.
3.3V Main and 5V Main PWM Output Capacitors
Selection of the output capacitors is also dependent on the
output inductor so some inductor analysis is required to
select the output capacitors.
One of the parameters limiting the converter’s response to a
load transient is the time required for the inductor current to
slew to it’s new level. Given a sufficiently fast control loop
design, the IPM6220 will provide either 0% or 94% duty
cycle in response to a load transient. The response time is
the time interval required to slew the inductor current from an
initial current value to the load current level. During this
interval the difference between the inductor current and the
transient current level must be supplied by the output
capacitor(s). Minimizing the response time can minimize the
output capacitance required. Also, if the load transient rise
time is slower than the inductor response time, as in a hard
drive or CD drive, this reduces the requirement on the output
capacitor.
The maximum capacitor value required to provide the full,
rising step, transient load current during the response time of
the inductor is:
Where: C
output inductor, I
is the input voltage, V
the drop in output voltage allowed during the load transient.
High frequency capacitors initially supply the transient
current and slow the load rate-of-change seen by the bulk
capacitors. The bulk filter capacitor values are generally
C
OUT
=
--------------------------------------------- -
OUT
V
IN
L
o
O
–
C. Normal operation is automatically restored
is the output capacitor(s) required, L
u
V
I
OUT
TRAN
TRAN
OUT
u
is the transient load current step, V
2
u
is output voltage, and 'V
--------------------
DV
I
TRAN
OUT
o
C.
O
OUT
is the
is
IN