MAX1707 Maxim Integrated Products, MAX1707 Datasheet - Page 13

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

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generates SCK to permit data transfer. A master device
communicates to the MAX1707 by transmitting the
proper 8-bit address (0x9A) followed by the 8-bit con-
trol byte. Each 8-bit control byte consists of a 3-bit
command code and 5 bits of data (see Table 1). Each
transmit sequence is framed by a START (A) condition
and a STOP (L) condition (see Figure 2). Each word
transmitted over the bus is 8 bits long and is always fol-
lowed by an acknowledge clock pulse.
When all the LEDs are off, the MAX1707 turns off the
charge pump and enters low-power shutdown mode.
When in shutdown, OUT is pulled to GND by an internal
5kΩ resistor, discharging the output capacitor. IN and
PIN are high impedance during shutdown, but the I
interface (powered from V
shutdown, send control byte 0x00 to the I
and drive STB high. To exit shutdown, enable any of
the LEDs with the I
The STB input is used to control the flash LEDs without
accessing the I
the flash LEDs are driven to the current set in the
STROBE register. Driving STB low overrides the flash
register settings. With STB high, the flash LEDs are
controlled by the I
control.
In case an LED fails or the cathode is shorted to GND,
the output overvoltage protection limits the output to
5V. When the MAX1707 detects the output voltage ris-
ing above 5V, it shuts off the charge pump. The charge
pump restarts once the output voltage has dropped to
4.9V.
To avoid constantly operating in overvoltage protection,
any unused LED cathode connection (M_, S_, or F_)
must be connected to OUT; this disables the corre-
sponding current regulator.
Thermal shutdown limits total power dissipation in the
MAX1707. When the junction temperature exceeds
+160°C, the MAX1707 turns off, allowing the IC to cool.
The MAX1707 turns on and begins soft-start after the junc-
tion temperature cools by 20°C. This results in a pulsed
output during continuous thermal-overload conditions.
Light-Management IC with Efficient 1x/1.5x/2x
Charge Pump for Backlight/Flash/RGB LEDs
Output Overvoltage Protection
2
C interface. When STB is driven low,
______________________________________________________________________________________
2
2
C interface or STB input.
C interface flash register and on/off
DD
) remains active. To enter
Thermal Shutdown
Shutdown Mode
STB Logic Input
2
C interface,
2
C
In 1x mode, the input ripple of the MAX1707 is negligi-
ble. When the charge pump is switching in 1.5x or 2x
mode, the input ripple depends on the load current and
the output impedance of the source supply. The worst-
case ripple occurs when the charge pump is operating
in 1.5x mode. The switching waveforms in the Typical
Operating Characteristics show the typical input ripple.
For noise-sensitive applications, input ripple can be
reduced by increasing the input capacitance.
Ceramic capacitors are recommended due to their small
size, low cost, and low ESR. Select ceramic capacitors
that maintain their capacitance over temperature and DC
bias. Capacitors with X5R or X7R temperature character-
istics generally perform well. Recommended values are
shown in the Typical Operating Circuit. Using a larger-
value input capacitor helps to reduce input ripple (see
the Input Ripple section).
The MAX1707 is a high-frequency switched-capacitor
regulator. For best circuit performance, use a solid
ground plane and place the capacitors as close to the
IC as possible. Connect the exposed pad to GND and
PGND, and allow sufficient copper area for cooling the
IC. Refer to the MAX1707 evaluation kit for an example
PC board layout.
PROCESS: BiCMOS
TOP VIEW
PGND
C1N
OUT
C2N
C1P
C2P
19
20
21
23
24
22
Applications Information
18
1
PC Board Layout and Routing
17
2
4mm x 4mm
MAX1707ETG
THIN QFN
16
3
Pin Configuration
15
Chip Information
4
Capacitor Selection
14
5
13
6
12
11
10
9
8
7
Input Ripple
F1
F2
F3
F4
M1
M2
13