MAX16826ATJ+C24 Maxim Integrated Products, MAX16826ATJ+C24 Datasheet - Page 20

• Manufacturer Part Number: MAX16826ATJ+C24
• Description: LED Drivers Programmable Four-St ring HB LED Driver w
• Manufacturer: Maxim Integrated Products

Specifications of MAX16826ATJ+C24

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The register file unit is used to store all the control infor-
mation from the SDA line and configure the MAX16826
for different operating conditions. The register file
assignments of the MAX16826 are in Table 2.
These registers are used to program LED string 1 to
LED string 4 current sink values. For each LED string,
CS1–CS4 inputs are connected to the source of the
external current sink FET and internally are connected
to the inverting input of the internal transconductance
amplifier. The noninverting input of this amplifier is con-
nected to the output of an internal DAC programmed
by these registers. As the DAC is incremented, its out-
put voltage decreases from 316mV to 97mV in 1.72mV
steps by the data written in the register 00h to 03h;
thus, the steady-state voltage at CS1–CS4 is given by
the following formula:
For example, if 00h is set to 20h, then the CS1 voltage is:
Set the switching regulator output voltage by connect-
ing FB to the center of a resistive voltage-divider
between the switching regulator output and GND. V
is regulated to a voltage from 876mV to 1.25V (typ) set
by the register 04h through the I
Programmable, Four-String HB LED Driver with
Output-Voltage Optimization and Fault Detection
Table 2. Register File Assignments
20
Registers 00h to 03h: String Current Programming
V
REGISTER
ADDRESS
CS1,2,3,4
______________________________________________________________________________________
0Ah
0Bh
0Ch
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
V
CS1
= 316mV - (1.72mV x RegisterValue[6:0])
= 316mV - 1.72mV x 32 = 265.3mV
Register 04h: Switching Regulator
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R
R
R
R
R
R
R
2
Output Programming
C interface.
Register File Unit
USED BIT
RANGE
[6:0]
[6:0]
[6:0]
[6:0]
[6:0]
[7:0]
[7:0]
[7:0]
[7:0]
[6:0]
[5:0]
[2:0]
[0]
FB
RESET
VALUE
00h
00h
00h
00h
00h
00h
00h
00h
00h
00h
00h
00h
—
The FB reference voltage can be decreased from 1.25V,
its maximum value, by approximately 2.9mV steps. The
steady-state voltage at FB then is regulated to:
These registers store the drain voltages of the external
current sink FETs. For each register, bits 6–0 are the
conversion data of the ADC outputs. Bit 7 is used to
show if the conversion is terminated by the ADC (indi-
cated by 0) or if there is an internal timeout (indicated
by 1). If the drain voltage exceeds the preset reference
voltage, the corresponding LED string fault bit is assert-
ed. See the Faults and Fault Detection section for more
information on the internal timeout function.
Bits 6-0 of this register store the voltage present at
OVP. This voltage is a scaled down version of the
switching regulator output voltage. Bit 7 is not used.
This register stores all the external events or fault infor-
mation such as overvoltage and shorted LED string
faults. The fault events are logged only if the system is
not in standby mode and their active states are longer
than one clock cycle. Cycle enable or power to clear the
fault status register. Initiating standby mode using the
I
2
C interface can also be used to clear the fault status
LED String 1 current programming value.
LED String 2 current programming value.
LED String 3 current programming value.
LED String 4 current programming value.
Switching regulator output voltage programming value.
LED String 1 external FET drain voltage ADC output.
LED String 2 external FET drain voltage ADC output.
LED String 3 external FET drain voltage ADC output.
LED String 4 external FET drain voltage ADC output.
OVP voltage, ADC output.
Fault status register.
Device standby command.
Device revision code.
Registers 05h to 08h: External Current-Sink
V
FB
= 1.25V - (2.91mV x 04h[6:0])
Register 0Ah: Fault Status Register
Register 09h: Switching Regulator
FET Drain Voltage ADC Readings
DESCRIPTION
Voltage ADC Output