MAX8798 datasheet(20/31 Pages) MAXIM

20 / 31 page

Internal-Switch Boost Regulator with

Integrated 3-Channel Scan Driver for TFT LCDs

______________________________________________________________________________________

High-Voltage Level-Shifting Scan Driver

The MAX8798 includes a 3-channel high-voltage (60V)

level-shifting scan driver that includes logic functions

necessary to drive row driver functions on the panel

glass (Figure 5). The driver outputs (CKV, CKVB, STVP)

swing between their power-supply rails (GON and

GOFF) according to the input logic levels on the block’s

inputs (STV, CPV, OE, and OECON) and the internal

logic of the block (Tables 3, 4). STV is the vertical sync

signal. CPV is the horizontal sync signal. OE is the output

enable signal. OECON is a timing signal derived from

OE that blanks OE if it stays high too long. These signals

have CMOS input logic levels set by the IN supply volt-

age. CKV and CKVB are complementary scan clock out-

puts. STVP is the output scan start signal. These output

signals swing from GON to GOFF that have a maximum

range of +45V and -25V. Their 10

Ω (typ) output imped-

ance enables them to swiftly drive capacitive loads. The

complementary CKV and CKVB outputs feature power-

saving, charge-sharing inputs (CKVCS, CKVBCS) that

can be used to save power by shorting each output to its

complement during transitions, making a portion of the

transition “lossless.”

PANEL GLASS

COLUMN DRIVER

SCAN DRIVER

SYSTEM

VIDEO

TIMING

STV

CKVB

STVP

CKV

CPV

CKV = SCAN CLK ODD

CKVB = SCAN CLK EVEN

STVP = HIGH-VOLTAGE STV

MAX8798

Figure 5. Scan Driver System Diagram

Table 3. STVP Logic

SIGNAL

LOGIC STATE

STV

OECON

CPV

STVP

Hi-Z

= Don’t care.

Table 4. CKV, CKVB Logic

SIGNAL

LOGIC STATE

STV

OECON

CPV

—

CKV

Toggle

CKVB

Toggle

= Don’t care. CS = Charge share state.

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