MC33099 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC33099

ALTERNATOR VOLTAGE REGULATOR

Motorola => Freescale 

MC33099

Alternator Regulator Biasing and Power Up/Down

The biasing of the regulator is derived from the Battery

terminal voltage Vbat. In the normal operating mode when the

ignition switch is ON and voltage Vign is greater than VTign

(about 1.25V), a 5.0V VDD voltage regulator biases the IC

logic and provides bias to a bandgap shunt voltage regulator.

The bandgap regulator maintains a reference voltage (Vref) of

approximately 2.0V with an internal negative temperature

coefficient (–TC) as well as a 1.25V Zero Temperature

Coefficient (OTC) reference voltage. Additional bias currents

and reference voltages, including a charge pump Gate

voltage Vg, are also generated from voltage Vbat. The

typically ignition ON drain current (IQ1(on)) is about 6.5 mA

at 25°C. When the ignition switch is OFF and voltage Vign is

less than VTign, the regulator is in a low current standby

mode, having a standby drain current of about 0.7mA

(IQ1(off)) at 25°C. During the sleep mode, some internal

voltage regulators and bias currents are either terminated or

minimized. However, the VDD regulator and the bandgap

voltage regulator continue to maintain voltages VDD for the

logic, the 2.0V Vref and the 1.25V reference voltage. In

addition, all logic is reset in the standby mode.

After switching the ignition switch to the ON position,

voltage Vign will exceed voltage VTign, causing comparator

Cign to switch states, prodiding an ignition–ON signal to the

Ingition Delay circuit. After an Ignition start Delay Time of

500mS, the Ignition Delay circuit activates additional current

for the VDD regulator and activates all other voltage

regulators and bias currents. After engine start, the LRC

mode is activated, independent of the phase frequency, or

independent of a Wide Open Throttle condition. When the

battery system voltage increases to Vset, the regulator

resumes the normal operational mode. After switching the

ignition switch to the OFF position, voltage Vign decreases

below voltage VTign, causing the comparator Cign to provide

an ignition–OFF signal to the Ignition Delay Circuit. After

phase frequency fph < f1 due to ignition turn OFF, supply

currents and voltages are reduced in the regulator to provide

the standby drain current drain. However, voltage VDD for

logic and voltage Vref for reference voltages remain active to

be able to sense an ignition input voltage.

In some applications, the ignition input is connected to the

low side of the fault lamp as shown in Fig. 1. When the lamp

driver circuitry is generating a lamp ON signal, a lamp polling

signal causes the Lamp Drain output to be periodically gated

OFF. As a result, voltge Vign >VTign during the lamp OFF

polling period, causing comparator Cign to periodically

provides an ignition–ON signal to the Ignition Delay Circuit.

During the Lamp On condition, the Ignition Delay Circuit

provides a minimum ignition turn–off delay (Tid(off)) such that

all currents and regulator voltages remain ON , between the

Lamp Off polling pulses.

Battery and Alternator Output Voltage Sensing

The system battery voltage is directly sensed by the

Remote input using a remote wire as a Kelvin connection.

The remote input resistance (Rrem) at the Remote input is

typically 68 kΩ. The voltage at the Remote Sense input (Vrs)

is a ratioed value of the Remote voltage (Vrem). The intended

ratio of Vrem/Vrs is about 7.45. The Battery terminal voltage

(Vbat) is also sensed as an internal Local voltage (Vl). A Local

Sense voltage (Vls) is a ratioed value of voltage Vl, where the

intended ratio of Vl/Vls is also 7.45. The Local internal

connection is provided for fault protection against the remote

wire being grounded, or exhibiting a high remote wire

resistance due to being disconnected or due to a corrosive or

lose connection. Thus the Local connection insures that

alternator regulation of the system voltage continues in well

defined states for all possible Remote input fault conditions.

Local and Remote Voltage Processing and Switching

During Remote operation, both the external Remote input

connection and internal Local connection senses

approximately the same regulated system voltage of Vset =

14.8 V. For this case, voltages Vrs and Vls are approximately

2V. Since the remote switching comparator Crs is referenced

to 0.6V, both switches S1 and S2 are OPEN and remain open

when voltage Vrs > 0.6V, or when voltage Vrem is greater than

the remote loss threshold voltage (VTrem). Voltage Vrs is

coupled to the input of a unity–gain combiner/buffer CB1.

Voltage Vls is buffered and coupled to the output of a

unity–gain Local Buffer (LB) and ratioed by the R5/(R4+R5)

resistor divider to provide an input voltage to a unity–gain

combiner/buffer CB2. Thus the voltage at the input of the

combiner CB2 is normally 0.8 Vls (or 1.6 V typically) while

voltage Vrs on the input of CB1 is typically 2.0 V. Since

voltage Vo reflects the highest voltage at the input of either

combiner, voltage Vo will be voltage Vrs in Remote operation

with Remote connected to Vbat. For this case, voltage Vrs is

filtered by a 300 Hz low pass filter and translated to the FB

buffer output. Voltage Vrs at the FB buffer output is then

compared to an Analog–to–Digital Converter output voltage

ramp (Vdac) for duty cycle regulation.

During a Remote fault condition when the remote sense

line is OPEN or grounded, voltage Vrs at the Remote Sense

input will be zero, causing comparator Crs to activate

switches S1 and S2 to a CLOSED position. As a result,

voltage Vls is coupled through buffer LB directly to the input

of combiner CB2. Since the voltage Vls on the input of

combiner CB2 is greater than voltage Vrs (= 0 V) on the input

of combiner CB1, voltage Vls is coupled to the output of the

combiners as voltage Vo. Thus in this fault case, voltage Vls

is filtered and translated to the FB buffer output for being

compared to voltage ramp Vdac for regulation.

During a remote fault condition in which the resistance of

the Remote sense wire increases due to the corrosion or a

lose connection, a finite external remote fault resistance

occurs causing voltage Vrem to decrease, but voltage Vrem

remains greater than voltage VTrem. As a result, switches S1

and S2 remain in an OPEN condition, while the system

voltage will increase due to the effective increase in the

Remote resistor divider ratio. As a result, voltage Vl

increases until the voltage at the input of combiner CB2 is

approximately 2V, or Vls is about 1.2(2V), or 2.25V due to the

R4/R5 divider ratio. Since the local divider ratio translates

voltage Vls to Vbat by about factor 7.4, the final regulated

output voltage for this condition is 7.4 (2.25)j, or 18.5V. This

is the scondary regulation voltage (Vset2). When the system

voltage increases to the Overvoltage Threshold (VTov), a fault

indication occurs by the lamp. Thus this particular Remote

fault condition produces a fault indication, but regulates to

prevent an extreme system overvoltage condition. When the

Remote fault resistance becomes great enough to cause

voltage Vrem < VTrem, the regulated system voltage returns to

the local regulation as described for an OPEN or grounded

Remote input.

8

MOTOROLA ANALOG IC DEVICE DATA

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