MC13181 View Datasheet(PDF) - Motorola => Freescale

Part Name

Description

Manufacturer

MC13181

Wireless Power Management Integrated Circuit

Motorola => Freescale 

3 Circuit Features

Circuit Features

3.1 Low Drop Out Regulators (LDO)

All three regulators are designed for use with low-value, low-cost bypass capacitors. Low ESR tantalum

capacitors are recommended (high performance ceramic capacitors with extremely low ESR, «1Ω, should

be avoided at regulator outputs to ensure stability, see Table 4 (Electrical Characteristics) for allowable

ESR range for each regulator). The output capacitors should be 1.0 µF minimum and should be mounted

close to the IC. Better transient performance can be achieved with a larger output capacitor. In general

turn-on and turn-off time will increase in proportion to the capacitor value. the regulators may not meet

specified turn-on time with a larger capacitor.

Table 6. LDO Regulators

LDO

Voltage

(V)

Current

(mA)

SEL

Cout

(µF)

LDO_1.85

LDO_2.65

LDO_3.0/3.3

1.85

30

-

1.0

2.65

65

-

1.0

3.0

60

high

1.0

LDO_3.0/3.3

3.3

60

low

1.0

Additional filter capacitors should be placed across each VCC input. A 0.1 µF ceramic close to the IC and a

1.0 µF tantalum (placement is less critical) are recommended.

All three regulators are designed for high Power Supply Rejection Ratio, low standby current, good line

and load regulation, and fast turn on.

The first regulator, LDO_1.85, supplies 1.85V. It is capable of a nominal output current of 30 mA. This

regulator is ideal for powering low-voltage digital or baseband circuitry.

The second regulator, LDO_2.65, supplies 2.65 V at up to 65 mA. This regulator is intended to supply

power for RF/IF circuitry. This regulator is optimized for slightly better close-in PSRR performance, and

derives its power from the VCC1 input pin. The input to the MC13180, which this LDC supplies current,

requires at least 2.55 V. The additional voltage of LDO_2.65 allows for a series resistor, shunt capacitor

filter into incorporate to further improve PSRR on that line. The resistor must be 0.220 Ω minimum, and

the capacitor 1.0 to 2.2 µF. The maximum resistor value should be chosen so that maximum current will

result in a voltage drop of 0.1 V or less.

The third regulator, LDO_3.0/3.3, can be set to either 3.0 V out to 3.3 V out through a single select line.

This output can source 60 mA. This regulator can be used to supply USB power or power an audio

CODEC or some other peripheral as needed. If the input voltage drops below the overhead needed for

regulation, the output of this regulator will track the input down to 2.7 V.

The LDO_1.85 and LDO_3.0/3.3 regulators derive their power from the VCC2 input pin. This allows

filtering to be tailored for the load circuitry, and to isolate the noisy digital (1.85 V) peripheral (3.0/3.3 V)

from the RF (2.65 V) and reference of the IC.

Each regulator has an independent, active-high enable line. This line can accept a “high” (to turn on the

regulator) input of 1.5 V up to either VCC, and can be tied directly to VCC if the enable function is not to be

used (shutdown will still function). If a given regulator is not needed in the application, the appropriate

enable input can be tied low (<1.5 V) and the output capacitor eliminated. Care should be taken if the

enable pin is to be driven from a processor powered by the corresponding regulator.

MOTOROLA

MC13181 Advance Information

13

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