33813 Datasheet, PDF (29/54 Pages) Freescale Semiconductor, Inc – One Cylinder Small Engine Control IC

Table 9. LAMPOUT SPI Configuration Register
7
6
5
4
3
2
1
0
Retry
x
Enable
(0)
(0)
x
OL
In- Rush
x
Current
Delay
Sink
(0)
Enable
(1)
(0)
(1)
PWM
Freq.
1
(0)
PWM
Freq.
0
(0)
The Retry Enable bit, bit 7, when set will allow the output to turn on for a short period and off for a long period when an over-
current condition is present. The open load (OL) current sink disable allow the current sink to be turned off when using the driver
as an LED driver to prevent ghosting, where the LEDs appears to be partially on due to the OL current sink. It can also be turned
off to measure the output device leakage. The Inrush delay bit, when set (by default for the Lamp driver) waits an additional time
before annunciating an over-current condition. This is done to allow for the inrush current of an incandescent lamp. The internal
PWM duty cycles (D/C) are controlled by the lower 7 bits in the corresponding SPI control register. The external duty cycles are
provided by the MCU on the input pin of the corresponding output driver.
Table 10. PWM Duty Cycles
Bits 1, 0
00
01
10
11
PWM Frequency
None or on ext. pin
100 Hz
1.0 KHz
On ext pin : 100
PWM D/C
None or on ext. pin
Internal
Internal
Internal
5.1.22 VRSP, VRSN Inputs, VRSOUT Output
The 33813 contains a VRS input conditioning circuit that employs a differential input. VRSP and VRSN are the positive and
negative inputs from the VRS. (see diagram on next page) Internal zener diode clamps to ground and V_CC limit the input voltage
to within the safe operating range of the circuit. It is important to provide external 15 k current limiting resistors to prevent damage
to the VRSP and VRSN inputs. (see R1 and R2 below) The VRS circuit conditions and digitizes the input from the crankshaft
mounted toothed wheel to provide an angle clock and RPM data to the MCU. This circuit provides a comparator with multiple
thresholds, which are programmed via the SPI to allow the VRS circuit to handle different sensors and the wide dynamic range
of the VRS output at engine speeds from crank to running. The output of this circuit is provided on the VRSOUT pin, which is a
5.0 Volt logic level signal to the MCU. The comparator threshold values can also be controlled automatically based on the input
signal amplitude. The output of the comparator contains a programmable one shot, noise blanking circuit. The time value of this
blanking pulse can be selected via the SPI as a percentage of the last input high (or low) pulse. The VRSOUT output can also
be divided and sent to the TACHOUT pin to drive a tachometer.
Table 11. SPI VRS Manual Configuration Register
SPI VRS Manual Parameters Configuration Register
Bits 7, 6, 5, 4
Threshold Values (nominal)
0000
0.01 - 28 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
0001
0.01 - 36 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
0010
3.0 - 36 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
0011
8.0 - 48 mV
(Tolerance not specified below 110 mV threshold. Only specified for monotonicity.)
Analog Integrated Circuit Device Data
Freescale Semiconductor
33813
29