34708 datasheet(67/159 Pages) FREESCALE

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Analog Integrated Circuit Device Data



Freescale Semiconductor

MC34708

Functional Block Description

7.5.6.3

Transient Response Waveforms

The transient load and line response are specified with the waveforms as depicted in Figure 18. Note that where the transient

load response refers to the overshoot only, so excluding the DC shift itself, the transient line response refers to the sum of both

overshoot and DC shift. This is also valid for the mode transition response.

Figure 18. Transient Waveforms

7.5.6.4

Short-circuit Protection (Feature no longer supported. See erratum 31.)

The higher current LDOs, and those most accessible in product applications, include a short-circuit detection and protection

(VDAC, VUSB, VUSB2, VGEN1, and VGEN2). The short-circuit protection (SCP) system includes debounced fault condition

detection, regulator shutdown, and processor interrupt generation, to contain failures and minimize the chance of product

damage. If an over-current (short-circuit) condition is detected, the LDO will be disabled by resetting its VxEN bit, while at the

same time, an interrupt SCPI will be generated to flag the fault to the system processor. The SCPI interrupt is maskable through

the SCPM mask bit.

The SCP feature is enabled by setting the REGSCPEN bit. If this bit is not set, then not only is no interrupt generated, but also

the regulators will not automatically be disabled upon a short-circuit detection. Note that by default, the REGSCPEN bit is not

set, so at startup, none of the regulators in an overload condition are disabled.

1us

0 mA

IMAX

ILOAD

ILOAD Stimulus for Transient Load

Response

10us

VNOM + 0.8V

VIN

VIN Stimulus for Transient Line

Response

Overshoot

IL = 0 mA

VOUT

VOUT for Transient Load Response

IL = IMAX

Overshoot

VNOM + 0.3V

Overshoot

Active Mode

VOUT

VOUT for Mode Transition Response

(VGEN2, VUSB2, VDAC)

Low Power Mode

Overshoot

IL < ILMAX

IL < ILMAXLP

IL < ILMAX

Active Mode

Mode Transition

Time

34708 Datasheet(PDF) 67 Page - Freescale Semiconductor, Inc

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