MAX16807 データシートの表示（PDF） - Maxim Integrated

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MAX16807

Integrated 8-Channel LED Driver with Switch-Mode Boost and SEPIC Controller

Maxim Integrated 

MAX16807

Integrated 8-Channel LED Driver with

Switch-Mode Boost and SEPIC Controller

LED Driver

4-Wire Interface

The MAX16807 also operates in stand-alone mode (see

the Typical Operating Circuits). For use with a microcon-

troller, the MAX16807 features a 4-wire serial interface

using DIN, CLK, LE, OE inputs and DOUT as a data out-

put. This interface is used to write the LED channels’ data

to the MAX16807. The serial-interface data word length is

8 bits (D0–D7). See Figure 3.

The functions of the five interface pins are as follows:

DIN is the serial-data input, and must be stable when

it is sampled on the rising edge of CLK. Data is shifted

in MSB first. This means that data bit D7 is clocked in

first, followed by seven more data bits, finishing with the

LSB (D0).

CLK is the serial-clock input that shifts data at DIN into the

MAX16807’s 8-bit shift register on its rising edge.

LE is the latch-enable input of the MAX16807 that trans-

fers data from the 8-bit shift register to its 8-bit output latch

(transparent latch). The data is latched on the falling edge

of LE (Figure 4). The fourth input (OE) provides output-

enable control of the output drivers. When OE is driven

high, the outputs (OUT0–OUT7) are forced to high imped-

ance without altering the contents of the output latches.

Driving OE low enables the outputs to follow the state of

the output latches. OE is independent of the operation

of the serial interface operation. Data can be shifted into

the serial-interface shift register and latched, regardless

of the state of OE. DOUT is the serial-data output that

shifts data out from the MAX16807’s 8-bit shift register on

the rising edge of CLK. Data at DIN propagates through

the shift register and appears at DOUT eight clock cycles

later. Table 1 shows the 4-wire serial-interface truth table.

Selecting External Component RSET to Set

LED Output Current

The MAX16807 uses an external resistor (RSET) to set

the LED current for outputs OUT0–OUT7. The minimum

allowed value of RSET is 330Ω, which sets the output

currents to 55mA. The maximum allowed value of RSET

is 5kΩ (IOUT_ = 3.6mA) and the maximum allowed

capacitance at SET is 100pF.

Use the following formula to set the output current:

R SET

=

18,000

I OUT _

where IOUT_ is the desired output current in milliamps

and the value for RSET is in ohms.

Overtemperature Cutoff

The MAX16807 contains an internal temperature

sensor that turns off all outputs when the die tempera-

ture exceeds +165°C. The outputs are enabled again

when the die temperature drops below +140°C. Register

contents are not affected, so when a driver is

overdissipating, the external symptom is the load LEDs

cycling on and off as the driver repeatedly overheats and

cools, alternately turning itself off and then back on again.

Table 1. 4-Wire Serial-Interface Truth Table

SERIAL CLOCK

LOAD

DATA INPUT SHIFT REGISTER CONTENTS INPUT

LATCH CONTENTS

BLANKING

INPUT

OUTPUT CONTENTS

CURRENT AT OUT_

INPUT

DIN

CLK D0 D1 D2 … Dn-1 Dn

LE D0 D1 D2 … Dn-1 Dn

OE

D0 D1 D2 … Dn-1 Dn

H

H R0 R1 … Rn-2 Rn-1

L

L R0 R1 … Rn-2 Rn-1

X

R0 R1 R2 … Rn-1 Rn

X X X… X X

L R0 R1 R2 … Rn-1 Rn

P0 P1 P2 … Pn-1 Pn

H P0 P1 P2 … Pn-1 Pn

L

P0 P1 P2 … Pn-1 Pn

X X X… X X

H

L L L… L L

L = Low Logic Level

H = High Logic Level

X = Don’t Care

P = Present State (Shift Register)

R = Previous State (Latched)

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