MAX16805_07 Datasheet, PDF (16/19 Pages) Maxim Integrated Products – EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback

EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
Thermal Foldback Clamp Level Register
(0x05), MAX16806
Thermal Foldback Clamp Level is a 3-bit register that
sets the minimum percentage of the LED current. Only
the first 3 bits of the data byte program the Thermal
Foldback Clamp Level register. The remaining 5 bits
are ignored. See Table 8. The factory-default register
value is 40%.
EEPROM Content Transfer Register (0x06)
The MAX16805/MAX16806 use the EEPROM Content
Transfer register to transfer data from the EEPROM to
the dynamic registers. A write command issued to this
register transfers data from the EEPROM to the dynam-
ic registers. Data bytes written to the EEPROM Content
Transfer register do not have any significance. At
power-up, the EEPROM content is automatically loaded
into the dynamic registers.
EEPROM Program Enable Register (0x08)
The EEPROM Program Enable register enables the
EEPROM for programming. Write to the EEPROM
Programming Enable register to initiate the EEPROM
programming cycle. Data written to the register does
not have any significance, however, it must be issued
following a write command [(0xFF), (0xCA)] to the
Password register.
Table 8. Thermal Foldback Clamp Level
THERMAL FOLDBACK
CLAMP LEVEL (%)
100
91
83
74
66
57
49
40
BIT 2
0
0
0
0
1
1
1
1
BIT 1
0
0
1
1
0
0
1
1
BIT 0
0
1
0
1
0
1
0
1
HEX
(0x00)
(0x01)
(0x02)
(0x03)
(0x04)
(0x05)
(0x06)
(0x07)
Applications Information
Programming the LED Current
The MAX16805/MAX16806 use a sense resistor across
CS+ and CS- to set the LED current. The differential
sense amplifier connected across R_SENSE provides
ground-loop immunity and low-frequency noise rejec-
tion. The LED current is given by the equation below:
I_LED = V_SENSE / R_SENSE
V_SENSE is programmable from 103mV to 198mV
using I²C.
Programming EEPROM
Set V_IN to 22V before initiating the EEPROM program-
ming. The MAX16805/MAX16806 use dynamic regis-
ters to program the EEPROM. Once the desired
dynamic registers have been updated with a setting,
write the data byte (0xCA) to the Password register
(0xFF). The data byte (0xCA) enables the EEPROM
programming mode. Any other data byte except the
(0xCA) disables the EEPROM programming mode. To
transfer data from dynamic registers to the EEPROM,
write to EEPROM Program Enable register (0x08).
Input Voltage Considerations
For proper operation, the minimum input voltage must
always be:
V_IN(MIN) > V_SENSE + V_FT(MAX) + ΔV_DO(MAX)
where V_FT(MAX) is the total forward voltage of all series
connected LEDs and ΔV_DO(MAX) is the maximum drop
output voltage.
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