MAX6970AUE Maxim Integrated Products, MAX6970AUE Datasheet - Page 6

• Manufacturer Part Number: MAX6970AUE
• Description: LED Drivers 8-Port 36V Constant- t-Current LED Driver
• Manufacturer: Maxim Integrated Products

Specifications of MAX6970AUE

• Number Of Segments: 16
• Low Level Output Current: 60000 uA
• Operating Supply Voltage: 3 V to 5.5 V
• Maximum Supply Current: 30000 uA
• Maximum Power Dissipation: 1702 mW
• Maximum Operating Temperature: + 125 C
• Mounting Style: SMD/SMT
• Package / Case: TSSOP EP
• Minimum Operating Temperature: - 40 C

The MAX6970 LED driver comprises a 4-wire serial inter-
face driving eight constant-current-sinking, open-drain
output ports. The outputs drive LEDs in either static or
multiplex applications (Figure 1). The constant-current out-
puts are guaranteed for current accuracy, not only with
chip-supply voltage variations (5V ±10% and 3V to 5.5V),
but also over a realistic range of driver output voltage drop
(0.8V to 2.5V). The drivers use current-sensing feedback
circuitry (not simple current mirrors) to ensure very small-
current variations over the full allowed range of output volt-
age (see the Typical Operating Characteristics).
The 4-wire serial interface comprises an 8-bit shift reg-
ister and an 8-bit transparent latch. The shift register is
written through a clock input, CLK, and a data input,
DIN, and the data propagates to a data output, DOUT.
The data output allows multiple drivers to be cascaded
and operated together. The contents of the 8-bit shift
register are loaded into the transparent latch through a
latch-enable input, LE. The latch is transparent to the
shift register outputs when high, and latches the current
state on the falling edge of LE.
Each driver output is an open-drain, constant-current
sink, which should be connected to the cathode of either
a single LED or a series string of multiple LEDs. The LED
anode can be connected to a supply voltage of up to
36V, independent of the MAX6970 supply, V+. The con-
stant-current capability is up to 55mA per output, set for
all eight outputs by an external resistor, R
8-Port, 36V Constant-Current LED Driver
6
(TSSOP)
5–12
_______________________________________________________________________________________
PIN
EP
13
14
15
16
1
2
3
4
OUT0–OUT7 LED Driver Outputs. OUT0 to OUT7 are open-drain, constant-current-sinking outputs rated to 36V.
NAME
DOUT
GND
CLK
DIN
SET
OE
V+
LE
—
Detailed Description
Ground
Serial-Data Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge.
Serial-Clock Input. Data is loaded into the internal 8-bit shift register on CLK’s rising edge.
Load-Enable Input. Data is loaded transparently from the internal shift register to the output latch while
LE is high. Data is latched into the output latch on LE’s falling edge and retained while LE is low.
Output-Enable Input. High forces outputs OUT0 to OUT7 high impedance without altering the contents
of the output latches. Low enables outputs OUT0 to OUT7 to follow the state of the output latches.
Serial-Data Output. Data is clocked out of the 8-bit internal shift-register to DOUT on CLK’s rising edge.
LED Current Setting. Connect SET to GND through a resistor (R
Positive Supply Voltage. Bypass V+ to GND with a 0.1µF ceramic capacitor.
Exposed Pad. Although not required, connecting EP to ground improves thermal performance.
SET
.
The serial interface on the MAX6970 is a 4-wire serial
interface, using four inputs (DIN, CLK, LE, OE) and a
data output (DOUT). This interface is used to write dis-
play data to the MAX6970. The serial-interface data
word length is 8 bits, D0–D7. See Figures 2 and 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 7 more data bits, finishing with the LSB D0.
CLK is the serial-clock input, which shifts data at DIN into
the MAX6970’s 8-bit shift register on its rising edge.
LE is the load input latch that transfers data from the
MAX6970 8-bit shift register to its 8-bit latch when LE is
high (transparent latch), and latches the data on the
falling edge of LE (Figure 2).
The fourth input provides output-enable control of the
output drivers. OE is high to force outputs OUT0 to
OUT7 high impedance without altering the contents of
the output latches, and low to enable outputs OUT0 to
OUT7 to follow the state of the output latches.
OE is independent of the serial-interface operation.
Data can be shifted into the serial-interface shift regis-
ter and latched regardless of the state of OE.
DOUT is the serial-data output, which shifts data out
from the MAX6970’s 8-bit shift register on the rising
edge of CLK. Data at DIN is propagated through the
shift register and appears at DOUT eight clock cycles
later. See Figure 2.
FUNCTION
SET
) to set the maximum LED current.
4-Wire Serial Interface
Pin Description