LT1950 Linear Technology, LT1950 Datasheet - Page 7

• Manufacturer Part Number: LT1950
• Description: Single Switch PWM Controller
• Manufacturer: Linear Technology

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PI FU CTIO S
BLANK (Pin 9): The BLANK pin is used to adjust the
leading edge blanking period of the current sense amplifier
during FET turn-on. Shorting the BLANK pin to ground
provides a default blanking period of approximately 110ns.
A resistor from the BLANK pin to ground increases the
blanking period up to 290ns for R
I
for the control loop. Connect this pin to the sense resistor
in the source of the external power MOSFET.
V
MOSFET gate drive circuit. Power can be supplied to this
pin by an external supply such as V
(the undervoltage lockout threshold for the gate driver
supply). For low V
regulator can be used to generate as much as 11V at the
V
voltages down to 3V while still supplying enough gate
drive for standard level MOSFETs.
GATE (PIN 12): The GATE pin is the output of a high current
gate drive circuit used to drive an external MOSFET. The
output is actively clamped to a max voltage of 13V if V
is supplied by a high voltage.
PGND (Pin 13): This is the ground connection for the high
current gate driver stage. See the Applications Informa-
tion section for recommendations on ground connec-
tions.
SENSE
IN2
IN2
U
pin. This allows the LT1950 to run with V
(Pin 11): The V
(Pin 10): The I
U
IN
U
SENSE
supply voltages an internal boost
IN2
pin is the supply pin for the
pin is the current sense input
BLANK
IN
, and must exceed 8V
= 75k.
IN
supply
IN2
BOOST (Pin 14): The BOOST pin is the NPN collector
output of the internal boost converter which can be used
to generate an 11V supply for the MOSFET gate driver
circuit. The boost converter runs with a fixed off-time of
0.5 s and a current limit of 125mA. The converter runs
until the V
the V
supplied externally, the BOOST pin should be shorted to
ground or left open.
V
LT1950. This pin must be closely bypassed to ground. If
V
will be fully functional, internal V
gate output will be enabled with a V
An internal undervoltage lockout threshold exists at ap-
proximately 2.6V on the V
voltages greater than 3V can be programmed using a
voltage divider on the SHDN pin.
V
maximum duty cycle of the gate driver circuit. The maxi-
mum duty cycle will be equal to (105/V
between 1.4V and 2.8V. This is a useful function to limit the
flyback voltage in a forward converter. If the maximum
duty cycle function is not used then the V
tied to ground.
IN
IN2
SEC
(Pin 15): The V
is generated using the BOOST pin then the LT1950
IN2
(Pin 16): The V
voltage drops below 10V. If the V
IN2
voltage exceeds 11V and then turns off until
IN
pin is the main supply pin for the
SEC
pin is used to program the
IN
pin. Undervoltage lockout
REF
IN
will be active and the
voltage as low as 3V.
SEC
SEC
LT1950
IN2
pin should be
)% for V
voltage is
sn1950 1950fs
7
SEC