Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsPMICsPMIC - LED driver DC-DC converter QFN 40 Surface-mount

LT3745-1

37451f

OPERATION

Inside the part, there are one 194-bit shift register

SR[0:193], one 1-bit frame select (FS) register, one 1-bit

enable LED channel (EN) register, sixteen 12-bit grayscale

(GS) registers, sixteen 6-bit dot correction (DC) registers,

one 1-bit over temperature (OT) flag register, and sixteen

1-bit LED fault flag registers. The input of the 194-bit shift

to the SDI signal. The output of the 194-bit shift register,

i.e., the output of the last bit SR[193] is connected to the

SDO signal. The SCKI signal shifts the SDI frame (GS or DC

frame) in and the SCKO signal shift the SDO frame (status

frame) out of the 194-bit shift register with their rising

edges. The LDI high signal latches the SDI frame (GS

DC frame) from the 194-bit shift register into correspond-

ing FS, EN, GS or DC registers, and loads the SDO frame

(status frame) from the OT and LED fault flag registers

to the 194-bit shift register at the same time. Therefore, a

daisy-chain type loop communication with simultaneous

writing and reading capability is implemented.

Figure 3 illustrates the timing relation among serial input

and serial

output signals in more detail. One DC frame fol-

lowed by another GS frame is sent through the LDI, SCKI,

and SDI signals. At the same time, two status frames are

received through the SCKO and SDO signals. The rising

edges of the SCKI signal shift a frame of 194-bit data at

100Ω

SCKO

LDO

CONTROLLER

CHIP 1

SCKO

–

SDO

–

100Ω

SDI

–

SDI

100Ω

SCKI

–

SCKI

LDI

SCKO

–

SDO

–

SCKI

LDI

SCK-

–

SDI

–

100Ω

CHIP 2

LT3745-1 LVDS Topology #1

SCKO

–

SDO

–

SCKI

LDI

SCK-

–

SDI

–

100Ω

CHIP N

SCKO

–

SDO

–

SCKI

LDI

SCK-

–

SDI

–

100Ω

SCKO

LDO

CONTROLLER

CHIP 1

SCKO

–

SDO

–

100Ω

SDI

–

SDI

100Ω

SCKI

–

SCKI

LDI

SCKO

–

SDO

–

SCKI

LDI

SCK-

–

SDI

–

100Ω

CHIP 2

LT3745-1 LVDS Topology #2

SCKO

–

SDO

–

SCKI

LDI

SCK-

–

SDI

–

100Ω

CHIP N

SCKO

–

SDO

–

37451 F01

SCKI

LDI

SCK-

–

SDI

–

Figure 1. Tw o Topologies of the LT3745-1 LVDS Serial Data Interface