ISL6729IB Intersil, ISL6729IB Datasheet - Page 5

• Manufacturer Part Number: ISL6729IB
• Description: IC CTRLR PWM SGL-ENDED 8-SOIC
• Manufacturer: Intersil

Specifications of ISL6729IB

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 2MHz
• Duty Cycle: 100%
• Voltage - Supply: 4.75 V ~ 5.25 V
• Buck: Yes
• Boost: Yes
• Flyback: Yes
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: -40°C ~ 105°C
• Package / Case: 8-SOIC (3.9mm Width)
• Frequency-max: 2MHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Electrical Specifications
NOTES:
Pin Descriptions
CLK - This is the oscillator timing control pin. The
operational frequency and maximum duty cycle are set by
applying a 5V amplitude clock signal to CLK. The logic high
duration defines the maximum ON time for the output. A
maximum clock rate up to 2.0MHz is possible.
COMP - COMP is the input to the PWM comparator and is
typically controlled through an external error amplifier.
CS - This is the current sense input to the PWM comparator.
The range of the input signal is nominally 0 to 1.0V and has
an internal offset of 100mV.
GND - GND is the power and small signal reference ground
for all functions.
OUT - This is the drive output to the power switching device.
It is a high current output capable of driving the gate of a
power MOSFET with peak currents of 1.0A. This GATE
output is actively held low when V
threshold.
V
operate from 4.75V to 5.25V. However, the accuracy of the
voltage clamp on the COMP signal, which determines the
over current threshold, is dependent on the accuracy of
VDD. A tight tolerance on VDD will result in a tight over
current threshold.
The total supply current will depend on the load applied to
OUT. Total I
and the average output current. Knowing the operating
frequency, f, and the MOSFET gate charge, Qg, the average
output current can be calculated from:
To optimize noise immunity, bypass V
ceramic capacitor as close to the V
possible.
I
PWM
Maximum Duty Cycle
Minimum Duty Cycle
3. Specifications at -40°C are guaranteed by design, not production tested.
4. This is the V
5. Guaranteed by design, not 100% tested in production.
OUT
DD
- V
=
DD
Qg
is the 5V power connection for the IC. The IC will
DD
×
f
DD
current is the sum of the operating current
PARAMETER
current consumed when the device is active but not switching. Does not include gate drive current.
5
Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application
schematic. V
DD
DD
is below the UVLO
DD
and GND pins as
to GND with a
DD
= 5V, CLK = 50kHz, T
(EQ. 1)
TEST CONDITIONS
ISL6729
A
= -40 to 105°C (Note 3), Typical values are at T
Ground Plane Requirements
Careful layout is essential for satisfactory operation of the
device. A good ground plane must be employed. A unique
section of the ground plane must be designated for high di/dt
currents associated with the output stage. V
bypassed directly to GND with good high frequency
capacitors.
Applications Information
Microcontrollers are becoming more popular for monitoring
and supervisory functions in power converters due to their
flexibility, capability, and declining prices. Many applications
would like to take advantage of this flexibility and use them
to perform the control loop function as well. There are many
examples of voltage mode control using digital signal
processing techniques. However, microcontrollers available
today do not have the execution speed required for peak
current mode control at the operational frequencies of
modern switch-mode power supplies. As such, they are
unable to detect the peak current and terminate the
switching cycle within the few nanosecond window required.
The ISL6729 provides the analog circuitry required to
perform peak current control, but delegates the oscillator
function to the microcontroller. This arrangement allows the
microcontroller to control soft-start, maximum duty cycle,
and operational frequency of the power converter, as well as
performing the traditional overhead functions such as fault
monitoring and system interface.
Application of the ISL6729 is similar to the ISL684x family of
PWM converters except that the input bias voltage has been
changed to 5V and the oscillator, reference, and error
amplifier functions have been removed. An external digital
clock signal, such as the PWM output of a microcontroller,
must be supplied to control the frequency and maximum
duty cycle. The frequency of the applied clock signal and the
frequency of operation of the PWM are identical. The duty
cycle of the clock is the maximum duty cycle of the PWM.
Soft-start may be accomplished by incrementing the duty
cycle of the applied clock signal from zero to the maximum
desired value in a time frame appropriate for the application.
MIN
-
-
TYP
99
-
A
= 25°C (Continued)
MAX
0
-
DD
should be
December 1, 2005
UNITS
FN9152.2
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