Datasheet

UC1851
UC2851
UC3851
Supply Voltage, +VIN (Pin 15)
Voltage Driven. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +32V
Current Driven, 100mA maximum. . . . . . . . . . . Self-limiting
PWM Output Voltage (Pin 12) . . . . . . . . . . . . . . . . . . . . . . . 40V
PWM Output Current, Steady-State (Pin 12) . . . . . . . . . 400mA
PWM Output Peak Energy Discharge . . . . . . . . . . . . 20µJoules
Driver Bias Current (Pin 14) . . . . . . . . . . . . . . . . . . . . . -200mA
Reference Output Current (Pin 16) . . . . . . . . . . . . . . . . -50mA
Slow-Start Sink Current (Pin 8) . . . . . . . . . . . . . . . . . . . . 20mA
V
IN Sense Current (Pin 11). . . . . . . . . . . . . . . . . . . . . . . . 10mA
Current Limit Inputs (Pins 6 & 7) . . . . . . . . . . . . . -0.5 to +5.5V
Stop Input (Pin 4) . . . . . . . . . . . . . . . . . . . . . . . . . -0.3 to +5.5V
Comparator Inputs
(Pins 1–7, 9–11, 16). . . . . . . . . . . . . . Internally clamped at 12V
Power Dissipation at T
A
= 25°C (Note 3). . . . . . . . . . . 1000mW
Power Dissipation at T
C
= 25°C (Note 3). . . . . . . . . . . 2000mW
Operating Junction Temperature. . . . . . . . . . . -55°C to +150°C
Storage Temperature Range . . . . . . . . . . . . . . -65°C to +150°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . . +300°C
Note 1:All voltages are with respect to ground, Pin 13.
Currents are positive-into, negative-out of the
specified terminal
Note 2:All pin numbers are referenced to DIL-18 package.
Note 3:Consult Packaging Section of Databook for thermal
limitations and considerations of package.
DIL-18, SOIC-18 (TOP VIEW)
J or N, DW Package
CONNECTION DIAGRAMS
PACKAGE PIN FUNCTIONS
FUNCTION PIN
COMP 1
START/UV 2
OV SENSE 3
STOP 4
RESET 5
CUR THRESH 7
CUR SENSE 8
SLOW START 9
RT/CT 10
RAMP 11
VIN SENSE 12
PWM OUT 13
GROUND 14
DRIVE BIAS 15
+VIN SUPPLY 17
5.0V REF 18
INV. INPUT 19
N.I. INPUT 20
PLCC-20, LCC-20
(TOP VIEW)
Q, L PACKAGE
ABSOLUTE MAXIMUM RATINGS (Note 1)
Unless otherwise stated, these specifications apply for TA = -55°C to +125°C for the
UC1851, -40°C to +85°C for the UC2851, and 0°C to 70°C for the UC3851; V
IN =
20V, R
T = 20kΩ, CT = .001 mfd, RR = 10kΩ, CR = .001mfd. Current Limit Threshold
= 200mV, T
A = TJ.
ELECTRICAL CHARACTERISTICS:
PARAMETER TEST CONDITIONS
UC1851 / UC2851 UC3851 UNITS
MIN TYP MAX MIN TYP MAX
Power Inputs
Start-Up Current V
IN = 30V, Pin 2 = 2.5V 4.5 6 4.5 6 mA
Operating Current V
IN = 30V, Pin 2 = 3.5V 15 21 15 21 mA
Supply OV Clamp V
IN = 20mA 333945333945 V
Reference Section
Reference Voltage T
J = 25°C 4.95 5.0 5.05 4.9 5.0 5.1 V
Line Regulation V
IN = 8 to 30V 10 15 10 20 mV
Load Regulation I
L = 0 to 10mA 1020 1030mV
Total Ref Variation Over Operating Temperature Range 4.9 5.1 4.85 5.15 V
Short Circuit Current V
REF = 0, TJ = 25°C -80 -100 -80 -100 mA
Oscillator
Nominal Frequency T
J = 25°C 47 50 53 45 50 55 kHz
Voltage Stability VIN
=
8 to 30V 0.5 1 0.5 1 %
Total Ref Variation Over Operating Temperature Range 45 55 43 57 kHz
Maximum Frequency
R
T = 2kΩ, CT = 330pF
500 500 kHz
2