SLUS329B − JUNE 1998 − REVISED FEBRUARY 2005
UC1854B
UC2854A, UC2854B
UC3854A, UC3854B
DESCRIPTION (continued)
The UC3854A/B products improve upon the UC3854 by offering a wide bandwidth, low offset current amplifier,
a faster responding and improved accuracy enable comparator, a VREF GOOD comparator, UVLO threshold
options (16 V/10 V for offline, 10.5 V/10 V for startup from an auxiliary 12 V regulator), lower startup supply
current, and an enhanced multiply/divide circuit. New features like the amplifier output clamps, improved
amplifier current sinking capability, and low offset VAC pin reduce the external component count while improving
performance. Improved common mode input range of the multiplier output/current amplifier input allow the
designer greater flexibility in choosing a method for current sensing. Unlike its predecessor, R
SET
controls only
oscillator charging current and has no effect on clamping the maximum multiplier output current. This current
is now clamped to a maximum of 2
×
I
AC
at all times which simplifies the design process and provides foldback
power limiting during brownout and extreme low line conditions.
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
ABSOLUTE MAXIMUM RATINGS
over operating free-air temperature range unless otherwise noted(1)
UCX854A, UCX854B
Supply voltage, VCC
GTDRV current, IGTDRV
GTDRV Current, IGTDRV
Input voltage
Input current
Power dissipation
Junction temperature, TJ
Storage temperature, Tstg
Continuous
50% duty cycle
VSENSE, VRMS, ISENSE MOUT
PKLMT
RSET, IAC, PKLMT, ENA
22
0.5
1.5
11
5
10
1
−55 to 150
−65 to 150
°C
C
UNIT
V
A
A
V
V
mA
W
Lead temperature, Tsol, 1,6 mm (1/16 inch) from case for 10 seconds
300
(1) Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is
not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. All voltages are with respect to
GND. Currents are positive into and negative out of, the specified terminal. ENA input is internally clamped to approximately 10 V.
RECOMMENDED OPERATING CONDITIONS
MIN
Supply voltage, VCC
UC1854X
Operating junction temperature, TJ
UC2854X
UC3854X
10
−55
−40
0
MAX
20
125
85
70
°C
C
UNIT
V
2
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