ncp5383 ON Semiconductor, ncp5383 Datasheet - Page 12

• Manufacturer Part Number: ncp5383
• Description: Two Phase Buck Controller With Integrated Gate Drivers And Avp
• Manufacturer: ON Semiconductor

APPLICATIONS INFORMATION
General
controller is specifically designed with the necessary
features for a high current power system. The IC consists
of the following blocks: High Performance Voltage Error
Amplifier, Precision Oscillator and Triangle Wave
Generators, and PWM Comparators. Protection features
include Undervoltage Lockout, Soft-Start, Overcurrent
Protection, Thermal Shutdown and Power Good Monitor.
High Performance Voltage Error Amplifier
and bandwidth. A capacitor from COMP to V
for stable unity gain test configurations.
Oscillator and Triangle Wave Generator
oscillator 's frequency is programmed by the resistance
connected from the R
usually form this resistance from two resistors in order to
create a voltage divider that uses the R
as the reference for creating the current limit setpoint
voltage. The oscillator frequency range is 100 kHz/phase
to 400 kHz/phase. The oscillator generates 2 triangle
waveforms (symmetrical rising and falling slopes)
between 1.3 V and 2.3 V. The triangle waves have a phase
delay between them such that for 2 phase operation the
PWM outputs are separated by 180 degrees.
PWM Comparators with Hysteresis
output signal at their non inverting input. Each comparator
receives one of the triangle waves offset by 1.3 V at it's
inverting input. During steady state operation, the duty
cycle will center on the valley of the triangle waveform,
with steady state duty cycle calculated by V
a transient event, both high and low comparator output
transitions shift phase to the points where the error
amplifier output intersects the down and up ramp of the
triangle wave.
The NCP5383 dual edge modulated multiphase PWM
The error amplifier is designed to provide high slew rate
A programmable precision oscillator is provided. The
Two PWM comparators receive the error amplifier
OSC
pin to ground. The user will
OSC
out
output voltage
FB
/V
is required
in
. During
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NCP5383
12
PROTECTION FEATURES
Undervoltage Lockout
During powerup, the input voltage to the controller is
monitored, and the PWM outputs and the soft-start circuit
are disabled until the input voltage exceeds the threshold
voltage of the UVLO comparator. The UVLO comparator
incorporates hysteresis to avoid chattering, since V
likely to decrease as soon as the converter initiates
soft-start. There is a separate undervoltage lockout
(UVLO) for the drivers that sense the V
Overcurrent Shutdown
within the IC. A comparator and latch makeup this
function. The inverting input of the comparator is
connected to the ILIM pin. The voltage at this pin sets the
maximum output current the converter can produce. The
ROSC pin provides a convenient and accurate reference
voltage from which a resistor divider can create the
overcurrent setpoint voltage. Although not actually
disabled, tying the ILIM pin directly to the ROSC pin sets
the limit above useful levels – effectively disabling
overcurrent shutdown. The comparator non inverting input
is the summed current information from the current sense
amplifiers. The overcurrent latch is set when the current
information exceeds the voltage at the ILIM pin. The
outputs are immediately, and the soft-start is pulled low.
The outputs will remain disabled until the V
removed and re-applied, or the ENABLE input is brought
low and then high.
Power Good Monitor
or 75% of Vfb for upper and lower thresholds respectively.
It is an open drain type output.
Soft-Start
soft-start. The soft-start circuit works by controlling the
ramp-up of the Vref voltage during powerup. The initial
soft-start pin voltage is 0 V. The soft-start sequence ends
when V
is an overcurrent shutdown, if V
threshold, or if V
Programming the Current Limit and Oscillator Frequency
is divided down with a resistor divider and fed into the
current limit pin ILIM. Calculate the total series resistance
to set the frequency and then calculate the individual values
for current limit divider. The series resistors RLIM1 and
RLIM2 sink current to ground. This current is internally
mirrored into a capacitor to create an oscillator. The period
is proportional to the resistance and frequency is inversely
proportional to the resistance.
An undervoltage lockout (UVLO) senses the V
A programmable overcurrent function is incorporated
NCP5383 has a power good monitor set at 125% of Vfb
The NCP5383 incorporates an externally programmable
The OSC pin provides a 2.0 V reference voltage which
SS
= 0.8 V. The soft-start pin is pulled to 0 V if there
CCP
is below the UVLO threshold.
CC
is below the UVLO
CCP
inputs.
CC
voltage is
CC
input.
CC
is