13892 datasheet(83/156 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

13892

FUNCTIONAL DEVICE OPERATION

SUPPLIES

REGULATORS GENERAL CHARACTERISTICS

The following applies to all linear regulators unless otherwise specified.

• Specifications are for an ambient temperature of -40 to +85 °C.

• Advised bypass capacitor is the Murata™ GRM155R60G225ME15 which comes in a 0402 case.

• In general, parametric performance specifications assume the use of low ESR X5R ceramic capacitors with 20% accuracy

and 15% temperature spread, for a worst case stack up of 35% from the nominal value. Use of other types with wider

temperature variation may require a larger room temperature nominal capacitance value to meet performance specs over

temperature. In addition, capacitor derating as a function of DC bias voltage requires special attention. Finally, minimum

bypass capacitor guidelines are provided for stability and transient performance. Larger values may be applied; performance

metrics may be altered and generally improved, but should be confirmed in system applications.

• Regulators which require a minimum output capacitor ESR (those with external PNPs) can avoid an external resistor if ESR

is assured with capacitor specifications, or board level trace resistance.

• The output voltage tolerance specified for each of the linear regulators include process variation, temperature range, static

line regulation, and static load regulation.

• The PSRR of the regulators is measured with the perturbed signal at the input of the regulator. The power management IC is

supplied separately from the input of the regulator and does not contain the perturbed signal. During measurements care must

be taken not to reach the drop out of the regulator under test.

• In the Low Power mode the output performance is degraded. Only those parameters listed in the Low Power mode section

are guaranteed. In this mode, the output current is limited to much lower currents than in the Active mode.

• Regulator performance is degraded in the extended input voltage range. This means that the supply still behaves as a

regulator and will try to hold up the output voltage by turning the pass device fully on. As a result, the bias current will increase

and all performance parameters will be heavily degraded, such as PSRR and load regulation.

• Note that in some cases, the minimum operating range specifications may be conflicting due to numerous set point and biasing

options, as well as the potential to run BP into one of the software or hardware shutdown thresholds. The specifications are

general guidelines which should be interpreted with some care.

• When a regulator gets disabled, the output will be pulled towards ground by an internal pull-down. The pull-down is also

activated when RESETB goes low.

•32 kHz spur levels are specified for fully loaded conditions.

• Short-circuit protection (SCP) is included on certain LDOs (see the SCP section later in this chapter). Exceeding the SCP

threshold will disable the regulator and generate a system interrupt. The output voltage will not sag below the specified voltage

for the rated current being drawn. For the lower current LDOs without SCP, they are less accessible to the user environment

and essentially self-limiting.

• The power tree of a given application must be scrubbed for critical use cases to ensure consistency and robustness in the

power strategy.

TRANSIENT RESPONSE WAVEFORMS

The transient load and line response are specified with the waveforms as depicted in Figure 25. Note that the transient load

response refers to the overshoot only, 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.

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