HIP6521_06 INTERSIL [Intersil Corporation], HIP6521_06 Datasheet - Page 7

• Manufacturer Part Number: HIP6521_06
• Description: PWM and Triple Linear Power Controller
• Manufacturer: INTERSIL [Intersil Corporation]

For an equation for the ripple current see the section under
component guidelines titled ‘Output Inductor Selection’.
Output Voltage Selection
The output voltage of the PWM converter can be
resistor-programmed to any level between V
However, since the value of R
the rest of the compensation components, it is advisable its
value is kept between 2kΩ and 5kΩ.
+3.3V
All linear regulators’ output voltages are set by means of
external resistor dividers as shown in Figure 4. The two
resistors used to set the voltage on each of the three linear
V OUT
V
1. The maximum r
2. The minimum I
3. Determine I
V
C
OUT3
C
OUT4
OUT3
FIGURE 4. ADJUSTING THE OUTPUT VOLTAGE OF ANY OF
i D
OC
OUT4
∆I is the output inductor ripple current.
IN
×
OVERCURRENT TRIP:
PWM
=
r DS ON
+
OCC
+
0.8
(
V
Q5
FIGURE 3. OVERCURRENT DETECTION
+
×
DS
-
⎛
⎜
⎝
THE FOUR REGULATORS (OUTPUTS 3 AND 4
PICTURED)
)
1
>
>
+
PEAK
V
CONTROL
I
Q4
OCSET
R
------- -
R P
SET
GATE
S
OCSET
DS(ON)
⎞
⎟
⎠
R
S4
for I
DRIVE
I
OCSET
40µA
×
OCSET
R
PEAK
R
S3
at the highest junction temperature.
from the specification table.
OCSET
R
P4
7
S1
> I
VCC
R
is affecting the values of
DRIVE3
P3
DRIVE4
OUT(MAX)
UGATE
PHASE
FB3
FB4
R
V PHASE
V
OCSET
V
OCSET
SET
+
IN
+ (∆I)/2, where
HIP6521
=
=
V
and 0.8V.
V IN V DS
IN
i
V
D
V
IN
+
= +5V
DS(ON)
–
–
V
SET
HIP6521
regulators have to meet the following criteria: their value
while in a parallel connection has to be less than 5kΩ, or
otherwise said, the following relationship has to be met:
There may be a second restriction on the size of the
resistors used to set the linear regulators’ output voltage
based on ACPI functionality. Read the ‘ACPI
Implementation’ section under ‘Application Guidelines’ to
see if this additional constraint concerns your application. To
ensure the parallel combination of the feedback resistors
equals a certain chosen value, R
equations:
V
V
Application Guidelines
Soft-Start Interval
The soft-start function controls the output voltages rate of rise
to limit the current surge at start-up. The soft-start function is
integrated on the chip and the soft-start interval is thus fixed.
Layout Considerations
MOSFETs switch very fast and efficiently. The speed with
which the current transitions from one device to another
causes voltage spikes across the interconnecting
impedances and parasitic circuit elements. The voltage
spikes can degrade efficiency, radiate noise into the circuit,
and lead to device overvoltage stress. Careful component
layout and printed circuit design minimizes the voltage
spikes in the converter. Consider, as an example, the
turn-off transition of the upper PWM MOSFET. Prior to
turn-off, the upper MOSFET was carrying the full load
current. During the turn-off, current stops flowing in the
upper MOSFET and is picked up by the lower MOSFET or
Schottky diode. Any inductance in the switched current
path generates a large voltage spike during the switching
interval. Careful component selection, tight layout of the
critical components, and short, wide circuit traces minimize
the magnitude of voltage spikes. See the Application Note
AN9908 for evaluation board drawings of the component
placement and printed circuit board.
There are two sets of critical components in a DC/DC
converter using a HIP6521 controller. The switching power
components are the most critical because they switch large
amounts of energy, and as such, they tend to generate
R
R
R
--------------------- -
R
OUT
FB
S
P
S
S
×
+
=
=
- feedback (reference) voltage, 0.8V.
R
R
V
--------------- -
-------------------------------- -
V
- the desired output voltage,
P
P
V
R
OUT
OUT
FB
<
S
5kΩ
×
×
–
V
V
R
FB
FB
FB
, where
FB
, use the following
October 16, 2006
FN4837.5