MC33094DW View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC33094DW

Ignition Control

Motorola => Freescale 

Freescale SMeCm3i3c0o94nductor, Inc.

Figure 7. Output Clamp Voltage

versus Temperature

15.2

15

VO = 0 V

ICL = 10 mA

14.8

14.6

14.4

14.2

14

-50

0

50

100

150

T, TEMPERATURE (°C)

Figure 8. Output Clamp Dynamic Impedance

versus Temperature

50

VO = 0 V

45

ICL = 12 mA

∆ICL = 2.0 mA

ZCL = ∆VCL/∆ICL

40

35

30

25

-50

0

50

100

150

T, TEMPERATURE (°C)

8.7

8.6

8.5

8.4

8.3

8.2

8.1

-50

Figure 9. Supply Drain Current

versus Temperature

Vin(-) = 0 V

VCC = 6.0 V

VD = 3.0 V

0

50

100

150

T, TEMPERATURE (°C)

Block Diagram Description (Figure 10)

The Band–Gap Reference generates a nominal 1.2 V

having very good stability with temperature variations. The

Band–Gap Reference conceptually provides a low

temperature drift voltage by summing a strongly negative

Temperature Coefficient (TC) voltage with an equally strong

positive TC voltage. The negative TC voltage element is a

result of a transistor emitter–to–base voltage while the

positive TC voltage is developed as a result of a positive TC

current imposed across a resistor. The positive TC current

relies on the matching of currents in different sizes of

transistors. The result is a very stable reference voltage

independent of temperature variations. The Band–Gap

Reference voltage provides a thermally stable voltage

reference for critically sensitive circuits within the IC. It also

sets the master bias current for all precision currents on the IC.

The Vr Zener Reference block contains a 6.75 V zener

regulator, which also exhibits a very low temperature

coefficient.

The VCC Comparator and Clamp block limits the VCC

voltage to one Vbe plus three zener drops in addition to

comparing the VCC voltage to 15 and 22 V. When the VCC

voltage is greater than either of these two values, the IC

changes the adaptive capacitor discharge rate and when

above 22 V the IC forces the coil current to shutdown. The

minimum VCC value the IC will operate at is 4.0 V and Vbat of

5.0 V. Below 7.5 V, the Vr reference is no longer maintained,

and the IC consumes excess power and excess voltage is

dropped in the external VCC resistor.

The Master Bias Current Reference block generates

precise currents used throughout the IC. The MB pin is held

at 1.2 V by a differential amplifier with feedback. Capacitive

loading on the MB pin reduces the effectiveness of the

internal dominant pole, and loading as modest as 200 pF

may cause the differential amplifier to oscillate.

The Input Voltage Comparator block requires an input

signal between ground and Vbat and detects the swing in the

input signal. The thresholds for the input comparator are

approximately 56.2% of Vbat for rising signals and 36% of

Vbat for falling signals. The input signal may come from a Hall

effect sensor or reluctor sensor on the distributor.

The Negative Edge Filter block is an inverting buffer for the

signal from the Input Voltage Comparator and has a time

constant of approximately 0.1 µs for rising edges and 500 µs

for falling edges.

The Adaptive Capacitor Charging and Sensing block

charges, discharges, and senses the adaptive capacitor

voltage. The adaptive capacitor has a single charge rate of

8.4 µA and two discharge rates. The 1.688 µA slow discharge

rate is used only during very high VCC operation and

8

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