VB027(6)-12 STMicroelectronics, VB027(6)-12 Datasheet - Page 4

• Manufacturer Part Number: VB027(6)-12
• Description: IC DVR PWR COIL 300V PENTAWATTHV
• Manufacturer: STMicroelectronics
• Series: VIPower™r

Specifications of VB027(6)-12

• Current - Output: 9A
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Through Hole
• Package / Case: Pentawatt-5 HV (Bent and Staggered Leads)
• Product: Electronic Ignition Drivers
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Operating Temperature: -
• Applications: -
• Number Of Outputs: -
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

APPLICATION NOTE
A. Current Limitation and Quasi Proportional
Base Driving
Due to the low resistance of the high energy ignition
coil, a current limitation system has to keep the
output current within the boundaries of the Safe
Operating Areas (Reverse and Forward), and limit
the energy stored in the coil.
The coil current is converted to a voltage by an
internal sensing resistor in series with the emitter of
the Darlington. This voltage is monitored by two
functional blocks: the current limiter block and the
quasi-proportional base current block, which perform
the functions described in the following paragraphs.
The current limiter block compares the monitored
voltage to an internal reference. When the internally
fixed threshold is reached, a feedback amplifier drives
the power Darlington to keep the voltage across the
sensing resistor (and hence also the coil current)
constant, until the falling edge of the input signal
starts the turn-off of the device. An active pull-down
Figure 5. Base driver operation
B. High Voltage Clamp
An integrated high voltage zener is connected
between the collector and the base of the output
stage of the Darlington. Its typical value is 360V, and
the voltage versus temperature characteristics are
shown in Figure 6.
4/7
I
base
is performed to accelerate the turn-off of the output
power.
The quasi-proportional base current block generates
a base current which increases proportionally to the
collector current. The base driver circuit must supply
a base current to the output power Darlington large
enough to turn on the device with an operating supply
voltage ranging from 4.5V to 5.5V. A conventional
driving circuit performs this function, supplying a
constant current to the device, regardless of the
output current value.
The driving circuit built inside the VB027 functions in
more complex manner, allowing energy saving and
lower stress of the low voltage supply circuit.
Figure 5 shows how the circuit works.
The current supplied to the V
close to the base current supplied to the output
Darlington, increases quasi-proportionally to the
output current.
In reality this clamp is not realized with a single high
voltage zener, but with a series of low voltage zeners,
allowing
without any process modification.
accurate trimming of the zener voltage
I
coil
d
pin, which is very