33813 Datasheet, PDF (24/54 Pages) Freescale Semiconductor, Inc – One Cylinder Small Engine Control IC

5 General IC Functional Description and Application
Information
5.1 Functional Pin Description
5.1.1 VPWR Supply Input
The VPWR pin is the battery input to the 33813 IC. The VPWR pin requires external reverse battery and adequate transient
voltage protection. All IC analog current and internal logic current is provided from the VPWR pin.
An over-voltage comparator monitors this pin and when an over-voltage condition is present all outputs and voltage regulators
are shut off for protection.
The VPWR pin should be bypassed to ground, as close to the IC as possible, with a 0.1 µF ceramic capacitor.
5.1.2 VPPREF Output
The VPPREF output pin is used to drive the base of an external regulator PNP pass transistor. The output of this V_PP regulator
supplies the input voltage to the two internal 5.0 Volt regulators. The V_PP regulator is a low drop-out (LDO) regulator that provides
a regulated output voltage when the input is greater than its specified voltage level, and follows the input voltage when it is below
its specified voltage level. It is not recommended that this voltage be brought off of the module PC board, because it may not
have adequate protection to prevent damage to the PNP pass transistor under short-to-ground or short-to-battery conditions.
5.1.3 VPPSENS Input
The VPPSENS pin is used to monitor the V_PP pre-regulator output voltage from the external pass transistor’s collector, and to
supply the input voltage to the V_CC and V_PROT regulators.
The VPPSENS pin should be bypassed to ground, as close to the IC as possible, with a 0.1 µF ceramic capacitor and a higher
value electrolytic capacitor in parallel.
5.1.4 VCC Output (5.0 V Supply)
The VCC regulator obtains its input voltage from the VPP pre-regulator. The VCC output supplies 5.0 V power to the system
MCU and other on-board peripherals.
A Power On Reset (POR) circuit monitors the V_CC output voltage level. When the V_CC voltage exceeds the V_CC(POR) threshold,
the RESETB line is held low for an additional delay time, t_(POR), and then brought to a logic one level.
An under-voltage (UV) circuit monitors the output of the V_CC regulator and when the voltage goes below the V_CC(UV) threshold
for more than the V_CC filter time, t_(VCC-UV), the RESETB line is asserted to a logic zero state and remains there until the POR
condition is met.
5.1.5 VPROT Output (5.0 V Protected Supply)
The VPROT regulator obtains its input voltage from the V_PP pre-regulator and its reference voltage from the VCC output. VPROT
tracks V_CC and is protected against shorts to ground, shorts to battery, over-current and over-temperature. The VPROT output
supplies 5.0 V power to any external sensors and other off-board peripherals. The V_PROT regulator on/off state can be controlled
via a bit in the SPI Control Registers. The VPROT output should be protected against ESD by means of a 0.1 µF ceramic
capacitor on the output and a higher value electrolytic capacitor in parallel.
Analog Integrated Circuit Device Data
Freescale Semiconductor
33813
24