33394 datasheet(18/44 Pages) FREESCALE

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33394

MOTOROLA ANALOG INTEGRATED CIRCUIT DEVICE DATA

battery (+18 V) and short to –2.0 V. Precautions must be taken

to protect the VREF pins from exposure to transients. See

Table 1 for recommended output capacitor parameters.

4.5.1. VREF Over Temperature Latch Off Feature

If either the VREF1, VREF2 or VREF3 outputs is shorted to

ground for any duration of time, an over temperature shut

down circuit disables the output source transistor once the

local die temperature exceeds +150

°C to +190°C. The output

transistor remains off until the locally sensed temperature is

°C to 20°C. below the trip off temperature. The output(s) will

periodically turn on and off until either the die temperature

decreases or until the fault condition is removed. If one of

these outputs goes into over—temperature shutdown, it will

not impact the operation of any of the other outputs (assuming

that no other package thermal or VPRE current limit

specifications are violated). Fault information is reported

through the SPI communication interface (see Figure 8).

4.6. Voltage Regulator (VDD3_3)

This linearly regulated +3.3 V +/–0.06 V voltage supply is

capable of sourcing 120 mA of steady state current from

VPRE (+5.6 V) for VBAT voltage from +4.0 V to +26.5 V (+45V

transient). This regulator incorporates current limit short

circuit protection and thermal protection. When no external

pass transistor is used the VDD3_3 and the VDD3_3FB pins

must be shorted together — see Figure 22. The current

capability of the VDD3_3 output can be increased by means

of an external pass transistor — see Figure 1. When the

external pass transistor is used the VDD3_3 internal short

circuit current limit does not provide the short circuit

protection. The voltage output is stable under all load/line

conditions. However, the designer must consider ripple and

high frequency filtering as well as regulator response when

choosing external components. See Table 1 in the

Applications Information section for recommended output

capacitor parameters.

NOTE :

Backfeeding into the VDD3_3 output can cause problems

during the power up sequence. Refer to the Electrical

Characteristics VDD3_3 Regulator Section for the maximum

allowed backfed current into the VDD3_3 output.

4.7. Voltage Regulator (VDDL)

The output voltage of the VDDL linear regulator is

adjustable by means of an external resistor divider.

This linearly regulated +/–2% core voltage supply uses an

external pass transistor and is capable of sourcing 40 mA

base drive current typically (see application circuit, Figure 1)

of steady state current. The collector of the external NPN pass

transistor is connected to VPRE (+5.6 V) for a VBAT voltage

from +7.5 V to +26.5 V (+45V transient). The voltage output is

stable under all load/line conditions. However, the designer

must consider ripple and high frequency filtering as well as

regulator response when choosing external components.

Also, the dynamic load characteristics of the microprocessor,

relative to CPU clock frequency changes must be considered.

An additional external pass transistor, for VDDL regulation in

the Boost mode, can be added between protected battery

voltage (see Figure 1) and VDDL, with its base driven by

VDDL_X. In that arrangement the 33394’s core voltage supply

operates over the whole input voltage range VBAT = +4.0 V

to +26.5 V (up to +45V transient). See Table 1 in the

Applications Information section for recommended output

capacitor parameters.

NOTES:

1. The use of an EXTERNAL pass device allows the power

dissipation of the 33394 to be reduced by approximately 50%

and thereby allows the use of a thermally efficient package

such as an HSOP 44 or QFN 44. The base drive control

signal (VDDL_B) is provided by on chip circuitry. The

regulated output voltage sense signal is fed back into the on

chip differential amplifier through pin VDDL_FB. The

collector of this external pass device should be connected to

VPRE to minimize power dissipation and adequately supply

400 mA. Proper thermal mounting considerations must be

accounted for in the PCB design.

2. Backfeeding into the VDDL output can cause problems

during the power up sequence. Refer to the Electrical

Characteristics VDDL Regulator Section for the maximum

allowed backfed current into the VDDL output.

4.8. Keep–Alive/Standby Supply (VKAM)

This linearly regulated Keep Alive Memory voltage supply

tracks the VDDL (+1.25 V to +3.3 V) core voltage, and is

capable of sourcing 50 mA of steady state current from VPRE

during normal microprocessor operation and 12 mA through

KA_VBAT pin during stand–by/sleep mode. The VKAM

regulator output incorporates a current limit short circuit

protection. The output requires a specific range of capacitor

values to be stable under all load/line conditions. See Table 1

in the Applications Information section for recommended

output capacitor parameters.

NOTE :

The source current for the VKAM supply output depends on

the sleep/wake state of the 33394.

4.9. Switched Battery Output (VSEN)

This is a saturated switch output, which tracks the VBAT and

is capable of sourcing 125 mA of steady state current from

VBAT. This regulator will track the voltage VBAT to less than

200 mV, and its output voltage is clamped at +17 V. The gate

voltage of the internal N—channel MOSFET is provided by a

charge pump from VBAT. There is an internal gate–to–source

voltage clamp. This regulator is short circuit protected and has

independent over—temperature protection. If this output is

shorted and goes into thermal shutdown, the normal operation

of all other voltage outputs is not impacted. This output is

controlled by the SPI VSEN bit.

NOTE:

A short to VBAT on VREF1, VREF2, VREF3 or VSEN will

not result in additional current being drawn from the battery

under normal (+8 V to +18 V) voltage levels. Under jumpstart

condition (VBAT = +26.5 V) and during load dump condition,

the device will survive this condition, but additional current

may be drawn from the battery.

4.9.1. VSEN Over Temperature Latch Off Feature

If the VSEN output is shorted to ground for any duration of

time, an over temperature shut down circuit disables the

output source transistor once the local die temperature

exceeds +150

°C to +190°C. The output transistor remains off

until the locally sensed temperature drops 5

°C to 20°C below

Freescale Semiconductor, Inc.

For More Information On This Product,

Go to: www.freescale.com

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