Power Management; A.ldo Usage - LG KG110 Service Manual

3. TECHNICAL BRIEF

3.2.4 Power Management

For direct battery supply connect, and to reduce external circuitry complexity the AD6548/9
features three Low Drop Out Regulators (LDOs). The three LDOs provide isolation of the
oscillators and sensitive circuits from unwanted power supply and cross coupled noise.
They also ensure the IC operation is robust over a wide range of power supply voltages.
For power management the LDOs are independently controlled via the 3 wire serial bus.

A.LDO Usage

The following table describes the LDO usage:
LDO1
Rx and Tx baseband
sections
The LDO outputs require external connection to the respective pins described in table 3, and
each requires decoupling capacitors.The LDOs are designed to be unconditionally stable
regardless of the capacitor's ESR.
LDO OP
VLDO1
VLDO2
VLDO3
LDO1 derives its input references from the crystal supply voltage (VCC_REF).
It is therefore expected that VCC_REF be supplied from a external LDO of nominal supply
voltage 2.75V
(e.g. ADP3330 or Analog Baseband IC: Vout=2.75V 1.4%)
LDO2
Main VCO
Table 3-2: Intended LDO Use
External Connection
VCC_FE, VCC_BBI, VCC_BBQ
No external Connections, except for decoupling
No external Connections, except for decoupling
Table 3-3: LDO Connections
14
LDO3
TX VCO