LT1509 Linear Technology, LT1509 Datasheet - Page 6
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LT1509
Manufacturer Part Number
LT1509
Description
Power Factor and PWM Controller
Manufacturer
Linear Technology
Datasheet
1.LT1509.pdf
(16 pages)
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6
TYPICAL PERFORMANCE CHARACTERISTICS
LT1509
PFC SECTION
GTDR1 (Pin 1): The PFC MOSFET gate driver is a fast
totem pole output which is clamped at 15V. Capacitive
loads like the MOSFET gates may cause overshoot. A gate
series resistor of at least 5 will prevent the overshoot.
GND2 (Pin 2): Power Ground. High current spikes occur
in this line when either GTDR1 or GTDR2 switches low.
GND1 (Pin 3): Analog Ground.
C
determines oscillator frequency. The oscillator ramp is 5V
and the frequency = 1.5/(R
PK
comparator is GND. To set current limit, a resistor divider
can be connected from V
CA
that senses and forces the line current to follow the
reference signal that comes from the multiplier by com-
manding the pulse width modulator. When CA
the modulator has zero duty cycle.
I
amplifier. This pin is clamped at – 0.6V by an ESD protec-
tion diode.
M
current output and the noninverting input of the current
amplifier. This pin is clamped at – 0.6V and 3V.
PIN
SENSE
SET
OUT
LIM
OUT
U
(Pin 4): The capacitor from this pin to GND and R
(Pin 8): This is the multiplier high impedance
(Pin 5): The threshold of the peak current limit
(Pin 6): This is the output of the current amplifier
FUNCTIONS
(Pin 7): This is the inverting input of the current
U
–100
–20
–40
–60
–80
120
100
80
60
40
20
0
R
0
SET
Voltage vs Current
–0.2
U
R
REF
SET
–0.4
SET
W
CURRENT (mA)
(For application help with the PFC portion of this chip, see the LT1248 data sheet)
to current sense resistor.
C
SET
–0.6
U
).
T
T
T
J
J
J
= 125 C
= 25 C
= –55 C
–0.8
LT1509 • TPC12
–1.0
OUT
is low,
SET
I
multiplier. It is a current input that is biased at 2V to
minimize the crossover dead zone caused by low line
voltage. At the pin, a 25k resistor is in series with the
current input, so that a lowpass RC can be used to filter out
the switching noise coming down from the line with a high
line impedance environment.
VA
amplifier. The output is clamped at 13.5V. When the
output goes below 2.5V, the multiplier output current is
zero.
OVP (Pin 11): This is the input to the overvoltage com-
parator. The threshold is 1.05 times the reference voltage.
When the comparator trips, the multiplier, which is quickly
inhibited, blanks PFC switching to prevent further over-
shoot. This pin is also the input to the PWMOK comparator
that releases the PWM soft start (SS2) after the PFC output
gets close to the final voltage and has a hysteresis of
approximately 150V for 382V PFC output.
V
low, V
circuitry and can source up to 5mA externally.
V
amplifier.
AC
REF
SENSE
OUT
(Pin 9): This is the AC line voltage sensing input to the
(Pin 12): This is the 7.5V reference. When V
REF
(Pin 10): This is the output of the voltage error
(Pin 14): This is the inverting input to the voltage
–360
–300
–240
–180
–120
–60
120
180
240
300
60
will stay at 0V. V
0
PK
–0.8
LIM
Pin Characteristics
–0.4
PK
LIM
VOLTAGE (V)
0
REF
biases most of the internal
0.4
T
T
T
J
J
J
= 125 C
= 25 C
= –55 C
LT1509 • TPC13
0.8
CC
goes