ltc4268cdkd-1-trpbf Linear Technology Corporation, ltc4268cdkd-1-trpbf Datasheet - Page 9

• Manufacturer Part Number: ltc4268cdkd-1-trpbf
• Description: High Power Pd With Synchronous Noopto Flyback Controller
• Manufacturer: Linear Technology Corporation

TYPICAL PERFORMANCE CHARACTERISTICS
PIN FUNCTIONS
SHDN (Pin 1): Shutdown Input. Used to command the
LTC4268-1 to present an invalid signature and remain
inactive. Connecting SHDN to V
resistance to an invalid value and disables other LTC4268-1
operations. If unused, tie SHDN to V
NC (Pin 2): No internal connection.
R
the LTC4268-1 maintains during classifi cation. Connect a
resistor between R
I
controlling the LTC4268-1 current limit behavior during
powered operation. For normal operation, fl oat I
enable I
input current limit. Note that the inrush current limit will
always be active. See Applications Information.
V
through the diode bridge. Pins 5, 6 and 7 must be electri-
cally tied together.
NC (Pin 8): No internal connection.
SG (Pin 9): Secondary Gate Driver Output. This pin pro-
vides an output signal for a secondary-side synchronous
switch. Large dynamic currents may fl ow during voltage
transitions. See the Applications Information for details.
LIM_EN
PORTN
CLASS
340
330
320
310
300
290
280
270
260
–50
Minimum PG On Time vs
Temperature
R
(Pin 3): Class Select Input. Used to set the current
LIMIT_HIGH
(Pins 5, 6, 7): Power Input. Tie to the PD Input
tON(MIN)
(Pin 4): Input Current Limit Enable. Used for
–25
= 158k
0
TEMPERATURE (°C)
current. Tie I
25
CLASS
50
and V
75
LIM_EN
100
PORTP
PORTN
42681 G28
125
PORTN
lowers the signature
. (See Table 2.)
to V
PORTN
.
300
250
200
150
100
50
0
–50
PG Delay Time vs Temperature
to disable
LIM_EN
–25
0
to
TEMPERATURE (°C)
R
R
25
PGDLY
PGDLY
V
to GND with 4.7μF or greater. This pin has a 20V clamp
to ground. V
turns on when V
In a conventional “trickle-charge” bootstrapped confi gura-
tion, the V
turn-on causing a benign relaxation oscillation action on
the V
t
programming resistor (R
for each cycle. See Applications Information for details.
ENDLY (Pin 12): Enable Delay Time Control. The enable
delay time is set by a programming resistor (R
GND and disables the feedback amplifi er for a fi xed time
after the turn-off of the primary-side MOSFET. This allows
the leakage inductance voltage spike to be ignored for
fl yback voltage sensing. See Applications Information
for details.
SYNC (Pin 13): External Sync Input. This pin is used to
synchronize the internal oscillator with an external clock.
The positive edge of the clock causes the oscillator to
discharge causing PG to go low (off) and SG high (on). The
sync threshold is typically 1.5V. Tie to ground if unused.
See Applications Information for details.
ON
CC
50
= 27.4k
= 16.9k
(Pin 11): Primary Switch Minimum On Time Control. A
(Pin 10): Converter Voltage Supply. Bypass this pin
CC
75
pin if the part does not start normally.
100
CC
42681 G29
CC
supply current increases signifi cantly during
125
has an undervoltage lockout function that
CC
is approximately 15.3V and off at 9.7V.
325
305
205
285
265
245
225
Ton
–50
Enable Delay Time vs
Temperature
R
) to GND sets the minimum time
ENDLY
–25
= 90k
0
TEMPERATURE (°C)
LTC4268-1
25
50
75
ENDLY
100
42681 G30
42681fa
9
) to
125