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LT1244CS8#TRPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
1
LT1241 Series
The LT
®
1241 series devices are 8-pin, fixed frequency,
current mode, pulse width modulators. They are improved
plug compatible versions of the industry standard UC1842
series. These devices have both improved speed and
lower quiescent current. The LT1241 series is optimized
for off-line and DC/DC converter applications. They con-
tain a temperature-compensated reference, high gain er-
ror amplifier, current sensing comparator and a high
current totem pole output stage ideally suited to driving
power MOSFETs. Start-up current has been reduced to
less than 250µA. Cross-conduction current spikes in
the output stage have been eliminated, making 500kHz
operation practical. Several new features have been incor-
porated. Leading edge blanking has been added to the
current sense comparator. Trims have been added to the
oscillator circuit for both frequency and sink current, and
both of these parameters are tightly specified. The output
stage is clamped to a maximum V
OUT
of 18V in the
on state. The output and the reference output are actively
pulled low during undervoltage lockout.
High Speed Current Mode
Pulse Width Modulators
■
Low Start-Up Current: < 250µA
■
50ns Current Sense Delay
■
Current Mode Operation: To 500kHz
■
Pin Compatible with UC1842 Series
■
Undervoltage Lockout with Hysteresis
■
No Cross-Conduction Current
■
Trimmed Bandgap Reference
■
1A Totem Pole Output
■
Trimmed Oscillator Frequency and Sink Current
■
Active Pull-Down on Reference and Output During
Undervoltage Lockout
■
High Level Output Clamp: 18V
■
Current Sense Leading Edge Blanking
D
U
ESCRIPTIO
S
F
EA
T
U
RE
U
S
A
O
PP
L
IC
AT
I
■
Off-Line Converters
■
DC/DC Converters
, LTC and LT are registered trademarks of Linear Technology Corporation.
+
–
+
–
1
2
FB
COMP
2.5V
2R
R
1V
1.5V
–
+
3
I
SENSE
BLANKING
1mA
5.6V
4
R
T
/C
T
OSCILLATOR
R
S
18V
7V
CC
5 GND
6 OUTPUT
8
V
REF
5V REF
MAIN BIAS
REFERENCE PULL-DOWN
OUTPUT
PULL-DOWN
REFERENCE ENABLE
1241 BD01
T
UV
LOCKOUT
W
IDAGRA
B
L
O
C
K
LT1241 Series
2
PARAMETER CONDITIONS MIN TYP MAX UNITS
Reference Section
Output Voltage I
O
= 1mA, T
J
= 25°C 4.925 5.000 5.075 V
Line Regulation 12V < V
CC
< 25V ● 320mV
Load Regulation 1mA < I
VREF
< 20mA ● –6 –25 mV
Temperature Stability 0.1 mV/°C
Total Output Variation Line, Load, Temp ● 4.87 5.13 V
Output Noise Voltage 10Hz < F < 10kHz, T
J
= 25°C50µV
Long Term Stability T
A
= 125°C, 1000 Hrs. 5 25 mV
Output Short-Circuit Current ● –30 –90 –180 mA
Oscillator Section
Initial Accuracy R
T
= 10k, C
T
= 3.3nF, T
J
= 25°C 47.5 50 52.5 kHz
R
T
= 13.0k, C
T
= 500pF, T
J
= 25°C 228 248 268 kHz
Voltage Stability 12V < V
CC
< 25V, T
J
= 25°C1%
Temperature Stability T
MIN
< T
J
< T
MAX
–0.05 %/°C
Amplitude T
J
= 25°C (Pin 4) 1.7 V
Clock Ramp Reset Current V
OSC
(Pin 4) = 2V, T
J
= 25°C 7.9 8.2 8.5 mA
Error Amplifier Section
Feedback Pin Input Voltage V
PIN1
= 2.5V ● 2.42 2.50 2.58 V
Input Bias Current V
FB
= 2.5V ● –2 µA
Open-Loop Voltage Gain 2 < V
O
< 4V ● 65 90 dB
Unity-Gain Bandwidth T
J
= 25°C 0.7 1.3 2 MHz
Power Supply Rejection Ratio 12V < V
CC
< 25V ● 60 dB
Output Sink Current V
PIN2
= 2.7V, V
PIN1
= 1.1V ● 26 mA
Output Source Current V
PIN2
= 2.3V, V
PIN1
= 5V ● –0.5 –0.75 mA
E
LECTR
IC
AL C CHARA TERIST
ICS
(Notes 1, 2)
A
U
G
W
A
W
U
W
ARB
S
O
LU
T
EXI T
I
S
Supply Voltage ........................................................ 25V
Output Current....................................................... ±1A*
Output Energy (Capacitive Load per Cycle)...............5µJ
Analog Inputs (Pins 2, 3)...............................–0.3 to 6V
Error Amplifier Output Sink Current...................... 10mA
Power Dissipation at T
A
≤ 25°C ................................ 1W
Operating Junction Temperature Range
LT124XC ............................................. 0°C to 100°C
LT124XI......................................... – 40°C to 100°C
LT124XM........................................ –55°C to 125°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)..................300°C
*The 1A rating for output current is based on transient switching
requirements.
ORDER PART
NUMBER
LT124XCJ8
LT124XCN8
LT124XCS8
LT124XIN8
LT124XIS8
LT124XMJ8
S8 PART MARKING
124X
124XI
WU
U
PACKAGE
/
O
RDER I FOR ATIO
COMP
FB
I
SENSE
R
T
/C
T
V
REF
V
CC
OUTPUT
GND
S8 PACKAGE
8-LEAD PLASTIC SO
N8 PACKAGE
8-LEAD PDIP
J8 PACKAGE
8-LEAD CERDIP
1
2
3
4
8
7
6
5
TOP VIEW
T
JMAX
= 125°C, θ
JA
= 100°C/W (J8)
T
JMAX
= 100°C, θ
JA
= 130°C/W (N8)
T
JMAX
= 100°C, θ
JA
= 150°C/W (S8)
3
LT1241 Series
PARAMETER CONDITIONS MIN TYP MAX UNITS
Error Amplifier Section
Output Voltage High Level V
PIN2
= 2.3V, R
L
= 15k to GND ● 5 5.6 V
Output Voltage Low Level V
PIN2
= 2.7V, R
L
= 15k to Pin 8 ● 0.2 1.1 V
Current Sense Section
Gain ● 2.85 3.00 3.15 V/V
Maximum Current Sense Input Threshold V
PIN3
< 1.1V ● 0.90 1.00 1.10 V
Power Supply Rejection Ratio ● 70 dB
Input Bias Current ● –1 10 µA
Delay to Output ● 50 100 ns
Blanking Time 100 ns
Blanking Override Voltage 1.5 V
Output Section
Output Low Level I
OUT
= 20mA ● 0.25 0.4 V
I
OUT
= 200mA ● 0.75 2.2 V
Output High Level I
OUT
= 20mA ● 12.0 V
I
OUT
= 200mA ● 11.75 V
Rise Time C
L
= 1nF, T
J
= 25°C5080ns
Fall Time C
L
= 1.0nF, T
J
= 25°C3060ns
Output Clamp Voltage I
O
= 1mA ● 18 19.5 V
Undervoltage Lockout
Start-Up Threshold
LT1241
● 9.0 9.6 10.2 V
LT1242/LT1244
● 15 16 17 V
LT1243/LT1245
● 7.8 8.4 9.0 V
Minimum Operating Voltage
LT1241/LT1243/LT1245 ● 7.0 7.6 8.2 V
LT1242/LT1244
● 9.0 10 11 V
Hysteresis
LT1241 1.6 2.0 V
LT1242/LT1244 5.5 6.0 V
LT1243/LT1245 0.4 0.8 V
PWM
Maximum Duty Cycle
LT1241/LT1244/LT1245 T
J
= 25°C4648%
LT1242/LT1243 T
J
= 25°C9496%
Minimum Duty Cycle ● 0%
Total Device
Start-Up Current ● 170 250 µA
Operating Current ● 710 mA
The ● denotes those specifications which apply over the full operating
temperature range.
Note 1: Unless otherwise specified, V
CC
= 15V, R
T
= 10k, C
T
= 3.3nF.
(Notes 1, 2)
E
LECTR
IC
AL C CHARA TERIST
ICS
Note 2: Low duty cycle pulse techniques are used during test to maintain
junction temperature close to ambient.
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LT1244CS8#TRPBF

Mfr. #:
Buy LT1244CS8#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Controllers Hi Speed C Mode Pulse Width Mods
Lifecycle:
New from this manufacturer.
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