Rev. A.8 - Oct., 2003
HPL5331
10
Copyright HIPAC Semiconductor, Inc.
www.hipacsemi.com
Application Information
General
The HPL5331 is a linear regulator and is capable of
sourcing or sinking current up to 3A. The HPL5331
has fast transient response, accurate output voltage
(small voltage offset, load regulation), active-low shut-
down control and fault protections (current-limit, ther-
mal shutdown). The HPL5331 is available in several
packages to meet different of power dissipation in
requirement various applications.
Output Voltage Regulation
The output voltage at VOUT pin tracks the reference
voltage applied at VREF pin. Two internal NPN pass
transistors controlled by separate high bandwidth er-
ror amplifiers regulate the output voltage by sourcing
current from VIN pin or sinking current to GND pin.
The base currents of the pass transistors are pro-
vided by VCNTL pin. An internal kelvin sensing
scheme use at the VOUT pin for perfect load regula-
tion at various load current. To prevent the two pass
transistors from shoot-through, a small voltage offset
is created between the positive inputs of the two error
amplifiers. This results in higher output voltage while
the regulator sinks light or heavy load current. Since
the HPL5331 exhibits very fast load transient response,
lesser amount of capacitors can be use. In addition,
capacitors with high ESR can also be use.
Shutdown and Soft-Start
The VREF pin is a dual-function input pin, acting as
reference input and shutdown control input. Apply-
ing and holding a voltage below 0.35V(typ.) to VREF
pin shuts down the output of the regulator. An NPN
transistor or N-channel MOSFET is used to pull down
the VREF while applying a “high” signal to turn on the
transistor. When shutdown function is active, the
two pass transistors are turned off and the imped-
ance of the VOUT is about 10M
Ω (typ.), sourcing or
sinking no current. When release the VREF pin, the
current through the resistor divider charges the soft-
start capacitor to initiate a soft-start cycle. The output
voltage tracks the rising VREF. The soft start process
limits the input surge current.
Thermal Shutdown
An thermal shutdown circuit limits the junction tem-
perature of the HPL5331. When the junction tempera-
ture exceeds TJ= +150oC, a thermal sensor turns off
both pass transistors, allowing the device to cool down.
The regulator starts to regulate again after the junc-
tion temperature reduces by 40oC, resulting in a
pulsed output during continuous thermal overload
conditions. The thermal limit designed with a 40oC
hysteresis lowers the average TJ during continuous
thermal overload conditions, extend life time of
HPL5331.
Current Limit
The HPL5331 monitors sourcing and sinking current,
and limits the maximum output current to prevent dam-
ages during overload or short-circuit, To increase
the input voltage of VIN or VCNTL will get higher
current-limit points.
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