33742 datasheet(24/65 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33742

FUNCTIONAL DEVICE OPERATION

OPERATIONAL MODES

FUNCTIONAL DEVICE OPERATION

SUPPLY VOLTAGE AT VSUP

The 33742 receives its operating voltage via the VSUP

pin. An external diode is needed in series with the VSUP pin

and the supply voltage to protect the SBC against negative

transients or from a reverse battery situation that can occur in

a vehicle application. The 33742 will operate from a supply

voltage input as low as 4.5 VDC to as high as 27 VDC. The

later voltage is often encountered during a vehicle jump-start.

The VSUP pin can tolerate automotive transient conditions

such as load dump to 40 V. The SBC is able to detect when

VSUP falls below 3.0 V typical. This undervoltage state is

detected and retained in the parts Mode Control Register

(MCR) as the BATFAIL bit. This detection capability is

available across all operating modes.

Note

For a detailed description of all the registers

mentioned in this section, refer to the section titled SPI

Interface And Register Description beginning on page 42.

The SBC incorporates a VSUP level early warning function,

which provides a maskable interrupt if the VSUP voltage level

falls below 6.0 V typical. Hysteresis is used to reduce false

detections. The early warning function works only in Normal

and Standby operation modes. An undervoltage at the VSUP

pin is reported in the Input/Output Register (IOR).

VDD REGULATOR

The VDD regulator provides a 5.0 V low dropout voltage

capable of supplying up to 200 mA with monitoring circuitry

for undervoltage detection and a reset function. The VDD

regulator is protected against overcurrent and short circuit

conditions. It has overtemperature detection and will set

warning flags (bit VDDTEMP in the MCR and INTR registers)

and has overtemperature shutdown with hysteresis.

V2 REGULATOR

The V2 regulator feature provides for a second 5.0 VDC

voltage source The internal V2 circuitry will drive an external

series pass transistor, substantially increasing the available

supply current. Two pins, the V2 and the V2CTRL, are used

to sense and drive the series pass transistor. The output

voltage is 5.0 V and tracks the VDD regulator. The MJD32C

transistor is recommended for use as the external pass

device. Other PNP transistors can be used but depending on

the device’s gain, an external resistor-capacitor network

might be needed. V2 is also the supply voltage for the on-

board CAN module. An undervoltage condition for the V2

voltage is reported in the IOR Register (bit V2LOW set to

logic [1] if V2 falls below 4.0 V typical).

HS VSUP SWITCH OUTPUT

The HS output is a 2.0

Ω typical switch tied to the VSUP

pin. It can power or bias external switches and their

associated pullup or put-downs or other circuitry. An example

is biasing a set of switches connected to the L0:L3 wake-up

input pins. The HS VSUP output current is limited to 200 mA

and is protected against short circuits conditions and will

report an overtemperature shutdown condition (bit HSOT in

the IOR register and bit HSOT-V2LOW in the INTR register).

The HS output “on” state is set by the HSON bit in the IOR

using an internal timer in the Sleep and Stop operating

modes. It can also be turned on in Normal or Standby modes

to drive loads or supply peripheral components. No internal

protection circuitry is provided, however. Dedicated chip

protection circuitry is required for inductive load applications.

The HS output pin should not go below -0.3 V.

BATTERY FAIL EARLY WARNING

Refer to the discussion under the heading, Supply Voltage

at VSUP above.

INTERNAL CLOCK

The 33742 has an internal clock used to generate all

timings (reset, watchdog, cyclic wake-up, filtering time, etc.).

There are two on-board oscillators;: a higher accuracy (±12

percent) oscillator used in Normal Request, Normal, and

Standby modes,; and a lower accuracy (±30 percent)

oscillator used during Sleep and Stop modes.

OPERATIONAL MODES

INTRODUCTION

The 33742 has four modes of operation, all controllable via

the SPI. The modes are Standby, Normal, Stop, and Sleep.

An additional temporary mode called Normal Request mode

is automatically accessed by the device after reset or wake-

up from Stop mode. A Reset mode is also implemented.

Special modes and configurations are possible for debug and

program microcontroller flash memory.

Table 7, page 25, offers a summary of the functional

modes.

STANDBY MODE

In Standby mode only the VDD regulator is ON. The V2

regulator is turned OFF by disabling the V2CTRL pin. Other

functions available are the L0:L3 inputs read through via the

SPI and HS output activation.

The CAN interface is not able to send messages. If a CAN

message is received, the CANWU bit is set. The watchdog

timer is running.

33742 Datasheet(PDF) 24 Page - Freescale Semiconductor, Inc

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