
Analog Integrated Circuit Device Data
Freescale Semiconductor
80
PC34708
Functional Block Requirements and Behaviors
LDO Regulators Description and Application Information
Figure 20. Transient Waveforms
7.5.5
Short-circuit Protection
The higher current LDOs, and those most accessible in product applications, include 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 a 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. However, the built-in current limiter will continue
to limit the output current of the regulator. Note that by default, the REGSCPEN bit is not set, so at startup, none of the regulators
in an overload condition are disabled.
7.5.6
Linear Regulator Supplies
7.5.6.1
VPLL
VPLL is provided for isolated biasing of the application processors PLLs for clock generation, in support of protocol and peripheral
needs. Depending on the application and power requirements, this supply may be considered for sharing with other loads, but
noise injection must be avoided and filtering added, if necessary to ensure suitable PLL performance. The VPLL regulator has a
dedicated input supply pin.
1us
0mA
Imax
Iload
Iload for Transient Load Response
10us
Vnom + 0.8V
Vin
Vin for Transient Line Response
Vnom + 0.3V
Overshoot
IL = 0mA
Vout
Vout for Transient Load Response
IL = Imax
Overshoot
IL < ILmaxlp
Vout
Vout for Mode Transition Response (VGEN1/2/3, VVIDEO, VCAM, VSD)
Overshoot
Active Mode
Low Power Mode
Active Mode
IL < ILmax
Mode
Transition
Time
IL < ILmax
VOUT Mode Transition Response (VGEN2, VUSB2, and VDAC)