ISL6441IRZ-TK Intersil, ISL6441IRZ-TK Datasheet - Page 13

• Manufacturer Part Number: ISL6441IRZ-TK
• Description: IC CTRLR PWM 1.4MHZ DUAL 28-QFN
• Manufacturer: Intersil

Specifications of ISL6441IRZ-TK

• Applications: Power Supplies
• Current - Supply: 2mA
• Voltage - Supply: 5.6 V ~ 24 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-QFN
• Rohs Compliant: YES
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ISL6441IRZ-TKTR

is detected for 2 consecutive clock cycles then the IC enters
a hiccup mode by turning off the gate drivers and entering
into soft-start. The IC will cycle 2x through soft-start before
trying to restart. The IC will continue to cycle through
soft-start until the overcurrent condition is removed.
Figure 17 shows this behavior.
.
Because of the nature of this current sensing technique, and
to accommodate a wide range of r
value of the overcurrent threshold should represent an
overload current about 150% to 180% of the maximum
operating current. If more accurate current protection is
desired, place a current sense resistor in series with the
lower MOSFET source.
Over-Temperature Protection
The IC incorporates an over-temperature protection circuit
that shuts the IC down when a die temperature of +150°C
is reached. Normal operation resumes when the die
temperatures drops below +130°C through the initiation of
a full soft-start cycle.
FIGURE 17. OVERCURRENT CONTINUOUS HICCUP MODE
FIGURE 16. OVERCURRENT TRIP WAVEFORMS
WAVEFORMS
13
DS(ON)
V
I
OUT2
SS2 2V/DIV
OUT2
PHASE2 10V/DIV
V
I
L
2V/DIV
OUT2
2V/DIV
2V/DIV
variations, the
2V/DIV
ISL6441
Implementing Synchronization
The SYNC pin may be used to synchronize two or more
controllers. When the SYNC pins of two controllers are
connected together, one controller becomes the master and
the other controller synchronizes to the master. A pull-down
resistor is required and must be sized to provide a low
enough time constant to pass the SYNC pulse. Connect this
pin to VCC_5V if not used. Figure 18 shows the SYNC pin
waveform operating at 4x the switching frequency.
Feedback Loop Compensation
To reduce the number of external components and to
simplify the process of determining compensation
components, both PWM controllers have internally
compensated error amplifiers. To make internal
compensation possible several design measures were
taken.
First, the ramp signal applied to the PWM comparator is
proportional to the input voltage provided via the VIN pin.
This keeps the modulator gain constant with variation in the
input voltage. Second, the load current proportional signal is
derived from the voltage drop across the lower MOSFET
during the PWM time interval and is subtracted from the
amplified error signal on the comparator input. This creates
an internal current control loop. The resistor connected to
the ISEN pin sets the gain in the current feedback loop. The
following expression estimates the required value of the
current sense resistor depending on the maximum operating
load current and the value of the MOSFET’s r
Choosing R
sample and hold circuitry is recommended but can operate
down to 2µA up to 100µA.
R
CS
≥
(
---------------------------------------------- -
I
MAX
CS
32μA
) r
(
DS ON
FIGURE 18. SYNC WAVEFORM
to provide 32µA of current to the current
(
)
)
SYNC 1V/DIV
DS(ON)
May 26, 2009
.
FN9197.3
(EQ. 6)