MC34708 datasheet(64/159 Pages) FREESCALE

64 / 159 page

Analog Integrated Circuit Device Data



Freescale Semiconductor

MC34708

Functional Block Description

SWBST can be controlled by SPI programming in PFM, PWM, and Auto mode. Auto mode transitions between PFM and PWM

mode based on the load current. By default SWBST is powered up in Auto mode.

Table 52. SWBST Mode Control

Parameter

Voltage

SWBST Mode

SWBSTMODE[1:0]

SWBSTSTBYMODE[1:0]

Off

PFM

Auto (default)

PWM

Table 53. SWBST Electrical Specifications

Characteristics noted under conditions BP = 3.6 V, VBUS = 5.0 V, -40 C  TA  85 C, unless otherwise noted. Typical values

at BP = 3.6 V and TA = 25 °C under nominal conditions, unless otherwise noted.

Symbol

Characteristic

Min

Typ

Max

Unit

Notes

SWITCH MODE SUPPLY SWBST

VSWBST

Average Output Voltage

•3.0 V < VIN < 4.5 V, 0 < IL < ILMAX

Nom-4%

VNOM

Nom+3%

(55)

VSWBSTACC Output Ripple

•3.0 V < VIN < 4.5 V 0 < IL < ILMAX, excluding reverse recovery of

Schottky diode

120 mV

Vp-p

SWBSTACC Average Load Regulation

•VIN = 3.6 V, 0 < IL < ILMAX

0.5

mV/mA

VSWBST

LINEAREG

Average Line Regulation

•3.0 V < VIN < 4.5 V IL = ILMAX

ISWBST

Continuous Load Current

•3.0 V < VIN < 4.5 V, VOUT = 5.0 V

380

ISWBSTPEAK Peak Current Limit

• At SWBSTIN, VIN = 3.6 V

1800

VSWBSTOS-

START

Start-up Overshoot, IL = 0 mA

500

tON-SWBST Turn-on Time

• Enable to 90% of VOUT IL = 0

2.0

fSWBST

Switching Frequency

2.0

MHz

VSWBST

TRANSIENT

Transient Load Response, IL from 1.0 to 100 mA in 1.0 µs

• Maximum transient Amplitude

300

VSWBST

TRANSIENT

Transient Load Response, IL from 100 to 1.0 mA in 1.0 µs

• Maximum transient Amplitude

300

VSWBST

TRANSIENT

Transient Load Response, IL from 1.0 to 100 mA in 1.0 µs

• Time to settle 80% of transient

500

µs

VSWBST

TRANSIENT

Transient Load Response, IL from 100 to 1.0 mA in 1.0 µs

• Time to settle 80% of transient

SWBST

Efficiency, IL = ILMAX

ISWBSTBIAS Bias Current Consumption

• PFM or Auto mode

µA

MC34708 Datasheet(PDF) 64 Page - Freescale Semiconductor, Inc

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