LT1247CS8 Linear Technology, LT1247CS8 Datasheet - Page 6

• Manufacturer Part Number: LT1247CS8
• Description: IC PWM CURRENT MODE 1MHZ 8SOIC
• Manufacturer: Linear Technology

Specifications of LT1247CS8

• Pwm Type: Current Mode
• Number Of Outputs: 1
• Frequency - Max: 1MHz
• Duty Cycle: 100%
• Voltage - Supply: 8.2 V ~ 25 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: Yes
• Operating Temperature: 0°C ~ 100°C
• Package / Case: 8-SOIC (3.9mm Width)
• Frequency-max: 1MHz
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

TYPICAL PERFOR
COMP (Pin 1): Compensation Pin. This pin is the output of
the Error Amplifier and is made available for loop compen-
sation. It can also be used to adjust the maximum value of
the current sense clamp voltage to less than 1V. This pin
can source a minimum of 0.5mA (0.8mA typ.) and sink a
minimum of 2mA (4mA typ.)
FB (Pin 2): Voltage Feedback. This pin is the inverting
input of the Error Amplifier. The output voltage is normally
fed back to this pin through a resistive divider. The
noninverting input of the Error Amplifier is internally
committed to a 2.5V reference point.
LT1246/LT1247
PI
6
V
C
Output Rise and Fall Time
U
CC
L
= 1nF
= 15V
FU
U
TIME 50ns/DIV
C
TI
60
50
40
30
20
10
0
O
Output Deadtime vs
Oscillator Frequency
0
U
S
OSCILLATOR FREQUENCY (kHz)
1246/7 G20
W
A
100
U
CE
5nF
500pF
C
2nF
LT1246 • TPC18*
HARA TERISTICS
100pF
Current Sense Delay
V
C
1nF
CC
L
= 1nF
1000
= 15V
C
TIME 50ns/DIV
I
current sense comparator. The trip point of the compara-
tor is set by, and is proportional to, the output voltage of
the Error Amplifier.
R
are set by connecting a resistor (R
and a capacitor (C
The rise time of the oscillator waveform is set by the RC
time constant of R
the output deadtime, is set by a combination of the RC time
constant and the oscillator sink current (8.2mA typ.).
SENSE
T
/C
T
(Pin 4) : The oscillator frequency and the deadtime
(Pin 3): Current Sense. This is the input to the
100
10
1246/7 G21
1
10k
Timing Resistor vs
Oscillator Frequency
C
T
V
T
J
=10nF
CC
= 25 C
= 15V
OSCILLATOR FREQUENCY (Hz)
T
T
) from R
and C
5nF
1nF
2nF
100k
T
. The fall time, which is equal to
Output Cross-Conduction
V
C
CC
L
T
= 15pF
/C
= 15V
100pF
T
to GND.
LT1246 • TPC19
T
200pF
) from V
500pF
TIME 50ns/DIV
1M
REF
to R
1246/7 G22
T
/C
T