U6083B Datasheet, PDF (7/12 Pages) TEMIC Semiconductors – PWM Power Control with Interference Suppression

U6083B
Pins 5 and Pin 6, Short-circuit Protection and Current Sensing
Short-circuit Detection and
Time Delay, t_d
Current Limitation
The lamp current is monitored by means of an external shunt resistor. If the lamp current
exceeds the threshold for the short-circuit detection circuit (V_T2 » 90 mV), the duty cycle
is switched over to 100% and the capacitor C₅ is charged by a current source of I_ch - I_dis.
The external FET again is switched off after the cut-off threshold (V_T5) is reached.
Switching on the FET again is possible after a power-on reset only. The current source,
I_dis, ensures that the capacitor C₅ is not charged by parasitic currents.
The time delay, t_d, is calculated as follows:
t_d = C₅ ´ V_T5/(I_ch - I_dis)
With C₅ = 100 nF and V_T5 = 10.4 V, I_ch =13 µA, I_dis = 3 µA, the time delay is as follows:
t_d = 100 nF ´ 10.4 V/(13 µA - 3 µA)
t_d = 104 ms
The lamp current is limited by a control amplifier to protect the external power transistor.
The voltage drop across the external shunt resistor acts as the measured variable. Cur-
rent limitation takes place for a voltage drop of V_T1 » 100 mV. Owing to the difference
V_T1 - V_T2 » 10 mV, it ensures that current limitation occurs only when the short-circuit
detection circuit has responded.
After a power-on reset, the output is inactive for half an oscillator cycle. During this time,
the supply voltage capacitor can be charged so that current limitation is guaranteed in
the event of a short-circuit when the IC is switched on for the first time.
Pins 7 and 8, Charge
Pump and Output
Pin 8 (output) is suitable for controlling a power MOSFET. During the active integration
phase, the supply current of the operational amplifier is mainly supplied by the capacitor
C₃ (bootstrapping). In addition, a trickle charge is generated by an integrated oscillator
(f₇ » 400 kHz) and a voltage doubler circuit. This permits a gate voltage supply at a duty
cycle of 100%.
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameters
Symbol
Value
Unit
Junction temperature
Ambient temperature range
Storage temperature range
T_j
150
°C
T_amb
-40 to +110
°C
T_stg
-55 to +125
°C
Thermal Resistance
Parameters
Junction ambient
Symbol
R_thJA
Value
120
Unit
K/W
7
4770A–AUTO–11/03