ISL6580CR Intersil, ISL6580CR Datasheet - Page 10

• Manufacturer Part Number: ISL6580CR
• Description: IC DRIVER HIGH SIDE FET 56-QFN
• Manufacturer: Intersil
• Type: High Side/Low Side Driverr

Specifications of ISL6580CR

• Input Type: Non-Inverting
• Number Of Outputs: 12
• On-state Resistance: 20 mOhm
• Current - Output / Channel: 25A
• Current - Peak Output: 35A
• Voltage - Supply: 5 V ~ 12 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 56-VQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

To understand the reduction of ripple current amplitude in
the multi-phase circuit, examine the equation representing
an individual channel’s peak-to-peak inductor current.
In Equation 1, V
voltages respectively, L is the single-channel inductor value,
and f
The output capacitors conduct the ripple component of the
inductor current. In the case of multi-phase converters, the
capacitor current is the sum of the ripple currents from each
of the individual channels. Compare Equation 1 to the
expression for the peak-to-peak current after the summation
of N symmetrically phase-shifted inductor currents in
Equation 2. Peak-to-peak ripple current decreases by an
amount proportional to the number of channels. Output-
voltage ripple is a function of capacitance, capacitor
equivalent series resistance (ESR), and inductor ripple
current. Reducing the inductor ripple current allows the
designer to use fewer or less costly output capacitors.
Another benefit of interleaving is to reduce input ripple
current. Input capacitance is determined in part by the
maximum input ripple current. Multi-phase topologies can
improve overall system cost and size by lowering input ripple
current and allowing the designer to reduce the cost of input
capacitance. The example in Figure 2 illustrates input
currents from a three-phase converter combining to reduce
the total input ripple current.
The converter depicted in Figure 2 delivers 36A to a 1.5V
load from a 12V input. The RMS input capacitor current is
I
I
C PP
PP
,
FIGURE 2. CHANNEL INPUT CURRENTS AND INPUT-
=
S
=
(
----------------------------------------------------- -
is the switching frequency.
V
(
----------------------------------------------------------- -
INPUT-CAPACITOR CURRENT
IN
V
IN
–
L f
V
–
CAPACITOR RMS CURRENT FOR 3-PHASE
CONVERTER
OUT
S
N V
L f
CHANNEL 1
V
IN
S
IN
OUT
) V
V
and V
IN
OUT
CHANNEL 2
) V
OUT
OUT
CHANNEL 3
1µs/DIV
10
are the input and output
(EQ. 2)
(EQ. 1)
ISL6580
5.9A. Compare this to a single-phase converter also
stepping down 12V to 1.5V at 36A. The single-phase
converter has 11.9A RMS input capacitor current. The
single-phase converter must use an input capacitor bank
with twice the RMS current capacity as the equivalent
three-phase converter.
Voltage Control Loop
One of the ISL6580 power stages in a multiphase converter
is used for voltage feed back. Output voltage is fed back to
this power stage which subtracts the reference voltage
(based on VID, see the VID table below) and converts the
error voltage to a binary number. The digital error number is
sent to the controller on the ERR line. The controller adds
offset proportional to the load current for the load line (see
next section on AVP) and passes the error number to the
digital Proportional, Integral, Derivative (PID) compensator.
The PID compensator is described in detail in a later section.
Output from the PID compensator drives the 6 phase digital
Pulse Width Modulator which produces the 6 PWM and
DRIVE signals that control switching of the power
MOSFETs.
COMPENSATOR
DIGITAL CONTROLLER
FIGURE 3. VOLTAGE CONTROL LOOP BLOCK DIAGRAM
PID
Σ
LOAD LINE AND
CURRENT
MODULATOR
SHARING
NDRIVE
PWM
IDIGn
ERR
SENSE AND A/D
POWER STAGE
CONVERTER
DRIVER
CURRENT
DRIVER
A/D
VID DAC
Σ
+
-
MOSFETS
COILS
CAPS
VOUT