33730 datasheet(16/27 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33730

FUNCTIONAL DEVICE OPERATION

OPERATION DESCRIPTION

FUNCTIONAL DEVICE OPERATION

OPERATION DESCRIPTION

INTRODUCTION

The 33730 has two supply inputs. The KA_VBAT pin is the

supply input for the standby regulators VKAM (and optionally

VDD3_SBY, see Table 6) and for the internal supply circuits.

The VBAT pin is the power input of the integrated buck

regulator, which steps-down the protected battery voltage

providing directly the 5.0V system supply VDDH. VDDH

provides power for the main linear regulator(s) VDDL, VDD3,

and also for the other module circuits requiring 5.0V supply

voltage (e.g. protected VREF1,2 outputs).

If the supply voltage ramps from zero volts up to its

nominal level, the 33730 will start at the latest when the

supply (battery) voltage reaches VSTUP at the KA_VBAT pin.

If the supply voltage ramps down, the 33730 will keep

operating (with degradation of the output voltage regulation)

down to VUVLO_f at the KA_VBAT pin. The VKAM output stays

operational down to VUVLO_f at the KA_VBAT pin.

The 33730 will operate in systems with and without

standby mode. In the Standby (sleep) mode of operation the

IC will draw maximum IQ quiescent current, assuming only

the VKAM is used as a standby output, and it is unloaded.

When VDD3 is used as an additional standby output the

quiescent current increases by approximately another

100

μA.

POWER UP

The 33730 will safely power up when the power is applied

simultaneously (hot plugged) or in the random sequence to

the KA_VBAT, VBAT and VIGN (or REGON) inputs.

POWER DOWN

The 33730 will safely power down when the power is

disconnected from any of the KA_VBAT, VBAT inputs or

when control signals the VIGN or REGON inputs go low.

UNDERVOLTAGE LOCK-OUT (UVLO)

There is an under-voltage lock-out feature implemented

into the IC. When the battery voltage at the KA_VBAT pin

falls below VUVLO_f the under-voltage comparator initiates the

power down sequence for the whole IC. The under-voltage

lock-out circuit has a VUVLO_hys hysteresis and 5.0μs glitch

filter in order to prevent spurious tripping its threshold level

and consequent system oscillations between the ON and

OFF states.

SWITCHING REGULATOR

The 33730 switching regulator is a fixed frequency

(externally adjustable) PWM voltage mode controller with

integrated low-RDS(ON) N-channel power MOSFET. This

architecture is widely flexible and provides a possibility to

optimize its operation over a wide range of input voltages.

The 33730 switching regulator provide the following features:

Adjustable Switching Frequency

The adjustable frequency feature provides the ability to

modify the switcher performance for optimized cost (higher

frequency, smaller, cheaper components) or higher efficiency

and better EMC performance (lower switching frequency for

reduced losses and EMI). The operating frequency of the

switching regulator can be adjusted by means of an external

resistor RF connected from the FREQ pin to ground (see

Figure 4).

Figure 4. Switching Regulator Frequency vs. RFreq

Value.

Adjustable Slew-rate

The adjustable slew-rate option allows, with selection of

the right switching frequency, optimization of the system for

EMC performance.

Over-voltage Lock-Out (Shut-Down)

The over-voltage lock-out (shut-down) feature turns the

switching regulator off when the input voltage exceeds the

VSHDN_r limit. This extends the 33730 capability to survive

the severe load dump conditions up to max VBAT.

Operation at 100% Duty Cycle

The internal charge pump is used to enhance the power

MOSFET gate when the switching regulator reaches 100%

duty cycle during the low battery conditions.

The switching regulator output voltage VDDH is regulated

to provide 5.0V @ 2.0A with ±2% accuracy and it is intended

to directly power the digital and analog circuits of the

Electronic Control Module (ECM). The switching regulator

output current is also used by the following linear regulators

VDD3_3, VDDL, and sensor supplies VREF1, and VREF2.

Frequency vs R

Freq

100

200

300

400

500

600

2040

6080

100

Freq [k ohm ]

33730 Datasheet(PDF) 16 Page - Freescale Semiconductor, Inc

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