Chapter 16 Dual Output Voltage Regulator (VREG3V3V2) Block Description
468
MC9S12C-Family / MC9S12GC-Family
Freescale Semiconductor
Rev 01.24
16.4.1
REG — Regulator Core
VREG3V3V2, respectively its regulator core has two parallel, independent regulation loops (REG1 and
REG2) that differ only in the amount of current that can be sourced to the connected loads. Therefore, only
REG1 providing the supply at V
DD
/V
SS
is explained. The principle is also valid for REG2.
The regulator is a linear series regulator with a bandgap reference in its Full Performance Mode and a
voltage clamp in Reduced Power Mode. All load currents flow from input V
DDR
to V
SS
or V
SSPLL
, the
reference circuits are connected to V
DDA
and V
SSA
.
16.4.2
Full-Performance Mode
In Full Performance Mode, a fraction of the output voltage (V
DD
) and the bandgap reference voltage are
fed to an operational amplifier. The amplified input voltage difference controls the gate of an output driver
which basically is a large NMOS transistor connected to the output.
16.4.3
Reduced-Power Mode
In Reduced Power Mode, the driver gate is connected to a buffered fraction of the input voltage (V
DDR
).
The operational amplifier and the bandgap are disabled to reduce power consumption.
16.4.4
LVD — Low-Voltage Detect
sub-block LVD is responsible for generating the low-voltage interrupt (LVI). LVD monitors the input
voltage (V
DDA
–V
SSA
) and continuously updates the status flag LVDS. Interrupt flag LVIF is set whenever
status flag LVDS changes its value. The LVD is available in FPM and is inactive in Reduced Power Mode
and Shutdown Mode.
16.4.5
POR — Power-On Reset
This functional block monitors output V
DD
. If V
DD
is below V
PORD
, signal POR is high, if it exceeds
V
PORD
, the signal goes low. The transition to low forces the CPU in the power-on sequence.
Due to its role during chip power-up this module must be active in all operating modes of VREG3V3V2.
16.4.6
LVR — Low-Voltage Reset
Block LVR monitors the primary output voltage V
DD
. If it drops below the assertion level (V
LVRA
) signal
LVR asserts and when rising above the deassertion level (V
LVRD
) signal LVR negates again. The LVR
function is available only in Full Performance Mode.
16.4.7
CTRL — Regulator Control
This part contains the register block of VREG3V3V2 and further digital functionality needed to control
the operating modes. CTRL also represents the interface to the digital core logic.
Summary of Contents for MC9S12C Family
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