4-Level or 2-Level Logic to High-Voltage

Level Shifter for TFT LCD TV Display

10

______________________________________________________________________________________

Sequential Operation

Connect CH to AGND and ST to VCC for four-level

sequential operation. If EN is LOW or VCC is less than its

STANDBY and the outputs connect to VCOM. After EN is

HIGH, VCC exceeds its UVLO and VLS exceeds its

UVLO, the outputs are ready to respond to logic inputs at

Ax and Bx. In sequential operation, the logic inputs and

corresponding output states sequence only in a prede-

fined order. In four-level operation, it is only possible to

progress from STATE 1 to STATE 2 or to STANDBY. The

same applies to the other transitions, including from

STATE 4 to STATE 1. Table 2 shows the logic states of

the level shifter in a sequential mode of operation.

Figure 3 shows the sequence of operation. Outputs

OAx and OBx always change in the same sequence.

Two-Level Operation

The MAX17079 also has a two-level output voltage

operation. Connect CH to VCC for two-level operation.

In two-level operation, the device transitions between

two states and the outputs can be connected only to

VH2 or VL2 or VCOM in STANDBY. Other than the start-

up condition, there is no way to distinguish between

sequential operation and combinational operation. If EN

is LOW or VCC is less than its UVLO or VLS is less than

its UVLO, the outputs are in STANDBY and the outputs

connect to VCOM. After EN is HIGH, VCC is greater

than its UVLO and VLS is greater than its UVLO, the

outputs are ready to respond to logic inputs at Ax.

Connect Bx to AGND, as the outputs respond only to

the rising and falling edge of Ax. The outputs transition

from VCOM to the specific output only on the rising

edge of Ax in sequential mode. In combinational mode,

the outputs transition from VCOM to the specific output

on either rising or falling edge of Ax. The following truth

table (Table 3) shows the output states.

EN

Ax

Bx

OAx

OBx

Figure 3. Sequential Mode Operation

STATE

Ax

Bx

OAx

OBx

STATE 1

H

H

VH1

VL1

STATE 2

H

L

VH2

VL2

STATE 3

L

H

VL1

VH1

STATE 4

L

L

VL2

VH2

Table 2. Truth Table Four-Level

Sequential Mode of Operation

HIGH (Ax)

OAx = VH2,

OBx = VL2

LOW (Ax)

OAx = VL2,

OBx = VH2

Table 3. Truth Table Two-Level Operation

x = Don’t care.