MAX1707 Maxim Integrated Products, MAX1707 Datasheet - Page 12

• Manufacturer Part Number: MAX1707
• Description: Light-Management IC
• Manufacturer: Maxim Integrated Products

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Table 4. RGB Ramp Rate
The flash LEDs are controlled either using the I
face or by pulsing the STB input low. There are two reg-
isters in the MAX1707 to set the flash current level. The
FLASH register sets the LED current when the I
face is used to pulse the flash LEDs, and the STROBE
register sets the LED current when the STB input is
pulsed. The current-level settings for the flash LEDs
range from 3.3mA to 100mA, with a default of 25.8mA
(see Tables 1, 2, and 3). The strobe register has priority
over the flash register when both strobe and flash are on.
The LED cathode connections (M_, S_, and F_) can be
connected together in any combination to allow the use
of higher current LEDs. For example, to drive a single
flash LED at up to 400mA, connect F1, F2, F3, and F4
together to the cathode of the flash LED.
To avoid constantly operating in overvoltage protection
mode, any unused LED cathode connection (M_, S_, or
F_) must be connected to OUT. This disables the corre-
sponding current regulator.
The three sub LED currents are controlled indepen-
dently by the I
Light-Management IC with Efficient 1x/1.5x/2x
Charge Pump for Backlight/Flash/RGB LEDs
Figure 2. I
*Default in bold.
12
CONTROL BYTE
(HEXADECIMAL)
SCK
SDA
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW
______________________________________________________________________________________
E0
E1
E2
E3
2
t
SU:STA
C Timing Diagram
RGB Color and Ramp-Rate Settings
A
2
t
HD:STA
C interface, allowing for use of a com-
RGB RAMP
RATE (A/s)
t
0.0572
0.0286
LOW
0.114
58.6
B
t
HIGH
R A M P TI M E FR O M OF F T O
F U L L BR I G H T N ESS ( m s )
t
SU:DAT
C
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE (OP/SUS BIT)
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW
0.512
1048
262
524
D
2
2
C inter-
C inter-
E
F
mon anode RGB LED. Thirty-two programmable bright-
ness levels (5 bits) per LED provide a total of 32k col-
ors. To smooth the transition between different
color/brightness settings, a controlled ramp is used
when the sub LED current level is changed, when the
sub LEDs are enabled, and when the LEDs are dis-
abled. The ramp rate is set to one of four settings with
the I
The MAX1707 contains a temperature-derating function
that automatically limits the LED current at high tempera-
tures in accordance with the recommended derating
curve of popular white LEDs. The derating function
enables the safe usage of higher LED current at room
temperature, thus reducing the number of LEDs required
to backlight the display. In camera-light applications, the
derating circuit protects the LEDs and PC board from
overheating. The derating circuit limits the LED current
by reducing the LED current above +40°C by approxi-
mately 1.7%/°C. The typical derating function character-
istic is shown in the Typical Operating Characteristics.
The temperature derating function is enabled/disabled
using the I
An I
MAX1707 to control LED brightness, flash, temperature
deration, and RGB ramp rate. The serial interface con-
sists of a serial data line (SDA) and a serial clock line
(SCK). Standard I
Figure 2 shows a timing diagram for the I
The MAX1707 is a slave-only device, relying upon a
master to generate a clock signal. The master (typically
a microprocessor) initiates data transfer on the bus and
t
HD:DAT
2
2
C interface (see Table 4).
C 2-wire serial interface is provided on the
G
2
C interface and is off by default.
Temperature-Derating Function
H
2
C write-byte commands are used.
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
I
J
K
I
2
C Interface
t
SU:STO
2
C protocol.
L
t
BUF
M