CM2841
150mA CMOS LDO WITH EN & PG
2004/05/14 Rev. 1.3
Champion Microelectronic Corporation
Page 5
DETAILED DESCRIPTION
The CM2841 family of CMOS regulators contain a PMOS pass transistor, voltage reference, error amplifier, over-current
protection, output short circuit protection, thermal shutdown, and power good function.
The P-channel pass transistor receives data from the error amplifier, over-current shutdown, short output protection, and thermal
protection circuits. During normal operation, the error amplifier compares the output voltage to a precision reference. Over-current
and Thermal shutdown circuits become active when the junction temperature exceeds 150℃, or the current exceeds 150mA.
During thermal shutdown, the output voltage remains low. Normal operation is restored when the junction temperature drops
below 120℃.
The CM2841 switches from voltage mode to current mode when the load exceeds the rated output current. This prevents
over-stress. The CM2841 also incorporates current fold-back to reduce power dissipation when the output is short-circuited. This
feature becomes active when the output drops below 0.95V, and reduces the current flow by 65%. Full current is restored when
the voltage exceeds 0.95V.
EXTERNAL CAPACITOR
The CM2841 is stable with an output capacitor to ground of 2.2µF or greater. It can keep stable even with higher or poor ESR
capacitors. A second capacitor is recommended between the input and ground to stabilize VIN. The input capacitor should be
larger than 0.1µF to have a beneficial effect. All capacitors should be placed in close proximity to the pins. A “quiet” ground
termination is desirable.
ENABLE
The Enable pin normally floats high. When actively, pulled low, the PMOS pass transistor shut off, and all internal circuits are
powered down. In this state, the quiescent current is less than 1µA. This pin behaves much like an electronic switch.
POWER GOOD
The CM2841 includes the Power Good feature. Normally, Pin 4 is “Low”, however, when the output is less than 15% of the
specified voltage, it pulls low. This can occur under the following conditions:
1)
Input Voltage too low
2)
During Over-Temperature
3)
During Over-Current
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