IR1152S
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© 2011 International Rectifier
IR1152 Pin Description
Pin COM: This is ground potential pin of the IC.
All internal devices are referenced to this point.
Pin COMP: External circuitry from this pin to
ground compensates the system voltage loop and
programs the soft start time. The COMP pin is
essentially the output of the voltage error amplifier.
The voltage loop error signal V
m
used in the control
algorithm is derived from V
COMP
(V
m
=V
COMP
–
V
COMP,START
). V
COMP
is actively discharged using an
internal resistance to below V
COMP,START
threshold
whenever the IC is pushed into Stand-by mode
(BOP or OLP condition) or UVLO/Sleep mode. The
gate drive output and logic functions of the IC are
inactive if VCOMP is less than V
COMP,START
. Also
during start-up, the VCOMP voltage has to be less
than V
COMP,START
in order to commence operation
(i.e. a pre-bias on VCOMP will not allow IC to
commence operation).
Pin ISNS: ISNS pin is tied to the input of the
current sense amplifier of the IC. The voltage at
this pin, which provides the current sense
information to the IC, has to be a negative voltage
wrt the COM pin. Also since the IC is based on
average current mode, the entire inductor current
information is necessary. A current sense resistor,
located below system ground along the return path
to the bridge rectifier, is the preferred current
sensing method. ISNS pin is also the inverting input
to the cycle-by-cycle peak current limit comparator.
Whenever V
ISNS
exceeds V
ISNS(PK)
threshold in
magnitude, the gate drive is instantaneously
disabled. Any external filtering of the ISNS pin must
be performed carefully in order to ensure that the
integrity of the current sense signal is maintained
for cycle-by-cycle peak current limit protection.
Pin BOP (Brown-out Protection): This pin is used
to sense the rectified AC input line voltage through
a resistor divider/capacitor network which is in
effect a voltage division and averaging network,
representing a scaled down signal of the average
rectified input voltage (average DC voltage + 2xf
AC
ripple). During start-up the BOP pin voltage has to
exceed V
BOP(EN)
in order to enable the IC to exit
Stand-by mode and enter normal operation. A
Brown-out situation is detected whenever the pin
voltage falls below V
BOP
and the IC is pushed into
Stand-by mode. Subsequently the pin has to
exceed V
BOP(EN)
for the IC to exit Stand-by and
resume normal operation.
Pin OVP/EN: The OVP/EN pin is connected to the
non-inverting input of the OVP(OVP) overvoltage
comparator shown in the block diagram and thus is
used to detect output overvoltage situations. The
output voltage information is communicated to the
OVP pin using a resistive divider. This pin also
serves the second purpose of an ENABLE pin. The
OVP/EN pin can be used to activate the IC into
“micropower sleep” mode by pulling the voltage on
this pin below the VSLEEP threshold. The OVP/EN
pin can be used to activate the IC into “micropower
sleep” mode by pulling the voltage on this pin below
the V
SLEEP
threshold.
Pin VFB: The converter output voltage is sensed
via a resistive divider and fed into this pin. VFB pin
is the inverting input of the output voltage error
amplifier. The non-inverting input of this amplifier is
connected to an internal 5V reference. The
impedance of the divider string must be low enough
that it does not introduce substantial error due to the
input bias currents of the amplifier, yet high enough
to minimize power dissipation. Typical value of
external divider impedance will be 2MΩ. The VFB
pin is also connected to the non-inverting input of
the OVP(VFB) overvoltage comparator as shown in
the block diagram and is used to detect output
overvoltage situations. Finally, VFB pin is also the
inverting input to the Open Loop comparator. The IC
is held in Stand-by Mode whenever VFB pin voltage
is below VOLP threshold. IC current consumption is
a few mA in this mode.
Pin VCC: This is the supply voltage pin of the IC
and sense node for the undervoltage lock out circuit.
It is possible to turn off the IC by pulling this pin
below the minimum turn off threshold voltage,
VCC(UVLO) without damage to the IC. This pin is
not internally clamped.
Pin GATE: This is the gate drive output of the IC.
This drive voltage is internally clamped to 13V(Typ)
and provides a drive current of ±0.75A peak with
matched rise and fall times.
