Only For Training And Service Purposes - LG KG290 Service Manual

♦ Voltage Regulators
- DBB Core Voltage Supply
The VCORE regulator is designed to be used as the core power supply for the DBB. With the
Hermes DBB its use is always appropriate. If the AD6721 VAPPCFG terminal is pulled up to the
main battery the pass device supply VAPP operates as a Core supply and can be used for this
purpose. Using VAPP as the core supply in this manner has three advantages. This mode frees
up the VCORE regulator for other applications such as use as a 1.8V memory supply. VAPP is
dynamically scalable that is its voltage can be changed as DBB clock frequencies are scaled.
And use of VAPP off loads power dissipation from the ABB to the pass device. This can be
important in power budgeting (see the Power Dissipation Budgeting Procedure section below).
- Serial Peripheral Supply
The nominal 2.8V VEXT regulator is meant to be a power supply used by various peripheral
devices in a handset. In the example shown in Figure 4 VEXT is a digital I/O supply for the
displays and the camera, a supply for the FM radio IC, and an I/O supply for the IrDA transceiver.
PSRAM, SRAM, NAND/NOR Flash Memory, SD/MMC, and DBB Memory Bus Supplies In the
example shown in Figure 4 the stack memory device uses the VMEM (at 2.8V) supply, VCORE
and the pass device VAPP supply. The SD or MMC card uses the VEXT supply. In the example
VAPP is programmed to be 1.8V nominal. Stack memory devices will have an SRAM, or PSRAM
and one or two types of Flash memory, NAND flash and/or NOR flash. Stack memory devices will
have a separate supply rail for each memory chip in the stack. The VCORE, VMEM and VAPP
pass device regulator are all appropriate choices for use as memory supplies.
DBB USB Transceiver Supply
The VUSB regulator supplies power to the USB transceiver in the DBB. Its input is the USB
VBUS line.
- Camera Supplies
In the example in Figure 4 the camera module has three supply rails. VGP set to 2.8V is the
camera analog supply used to power the camera's sensor. VEXT is used as the I/O supply. And
VAPP set to 1.8V is the camera digital supply. The camera module used in the example is a type
that does both image sensing and image processing. VGP and VAPP are both programmable
voltage supplies.
Copyright © 2007 LG Electronics. Inc. All right reserved.

Only for training and service purposes

3. TECHNICAL BRIEF
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LGE Internal Use Only