Datasheet
3
UC2855A/B
UC3855A/B
ELECTRICAL CHARACTERISTICS:
Unless otherwise specified: VCC = 18V, RVS = 23k, CT = 470pF, CI = 150pF, VRMS
= 1.5V, IAC = 100µA, I
SENSE
= 0V, CAO = 4V, VAOUT= 3.5V, VSENSE = 3V. –40°C to 85°C (UC2855A/B), 0°Cto70°C
(UC3855A/B).
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
Current Amplifier
Input Offset Voltage V
CM
= − 2.5V −44mV
Input Bias Current (Sense) V
CM
= 2.5V −500 500 nA
Open Loop Gain V
CM
= 2.5V, VOUT =2to6V 80 110 dB
V
OUT High I
LOAD
= −500µA6V
V
OUT Low I
LOAD
= 500µA 0.3 0.5 V
Output Short Circuit Current V
OUT
=0V 1 3 mA
Common Mode Range −0.3 5 V
Gain Bandwidth Product F
IN
= 100kHz, 10mV, P–P, T
A
= 25°C 2.5 5 MHz
Reference
Output Voltage I
REF
= 0mA, TA = 25°C 7.388 7.5 7.613 V
I
REF
= 0mA 7.313 7.5 7.688 V
Load Regulation I
REF
=1to10mA −15 15 mV
Line Regulation VCC = 15 to 35V −10 10 mV
Short Circuit Current REF = 0V 20 45 65 mA
Oscillator
Initial Accuracy T
A
=25°C 170 200 230 kHz
Voltage Stability V
CC
=12to18V 1 %
Total Variation Line, Temp. 160 240 kHz
Ramp Amplitude (P–P) Outputs at 0% duty cycle 4.7 5.7 V
Ramp Valley Voltage 1.1 1.6 V
Enable/OVP/Current Limit
Enable Threshold 1.8 2.2 V
OVP Threshold 7.5 7.66 V
OVP Hysteresis 200 400 600 mV
OVP Propagation Delay 200 ns
OVP Input Bias Current V= 7.5V 1 10 µA
PK
LIMIT Threshold 1.25 1.5 1.75 V
PK
LIMIT Input Current V
PKLIMIT
= 1.5V 100 µA
PK
LIMIT Prop. Delay 100 ns
Soft Start
Soft Start Charge Current -10 -13 -20 mA
Soft Start Discharge Current 2 10 20 mA
Multiplier
Output Current - IAC Limited IAC = 100µA, VRMS = 1V −235 −205 −175 µA
Output Current - Zero IAC = 0µA −2 −0.2 2 µA
Output Current - Power Limited VRMS = 1.5V, VAOUT = 5.5V −250 −209 −160 µA
Output Current VRMS = 1.5V, VAOUT = 2V −26 µA
VRMS = 1.5V VAOUT = 5V −190 µA
VRMS = 5V, VAOUT = 2V −3 µA
VRMS = 5V, VAOUT = 5V −17 µA
Gain Constant Refer to Note 1 −0.95 −0.85 −0.75 1/V