MAX6948B MAXIM [Maxim Integrated Products], MAX6948B Datasheet - Page 12

• Manufacturer Part Number: MAX6948B
• Description: High-Efficiency PWM LED Driver with Boost Converter and Five Constant-Current GPIO Ports
• Manufacturer: MAXIM [Maxim Integrated Products]

High-Efficiency PWM LED Driver with Boost
Converter and Five Constant-Current GPIO Ports
The MAX6948B boost converter has 10-bit PWM opera-
tion using an internal 125kHz clock. This yields a PWM
period of 1024/125k = 8.192ms. PWM operation allows
the user to adjust the LED intensity and lower the average
current by enabling and disabling the boost converter at
a selectable rate. This rate is set using the boost-con-
verter output PWM registers (Tables 4, 5). The duty cycle
ranges from 0/1024 (no intensity or off) to 1023/1024 (full
intensity). Eight of the 10 bits, which include the MSB, are
Table 4. Boost-Converter Output PWM (MSB) Register Format (0x20)
X = Don’t care.
Table 5. Boost-Converter Output PWM (LSB) Register Format (0x21)
Table 6. Boost-Converter Status Register Format (0x22)
12
REGISTER BIT
REGISTER BIT
REGISTER BIT
D7, D6, D5
D7–D2
D4
D3
D2
D1
D0
D1
D0
D7
D6
D5
D4
D3
D2
D1
D0
Thermal shutdown
Boost-Converter Output PWM
DESCRIPTION
Schottky open
Boost standby
Current limit
Overvoltage
DESCRIPTION
DESCRIPTION
Reserved
Reserved
Bit 1
Bit 0
Bit 9
Bit 8
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Boost Converter
VALUE
000
0
1
0
1
0
1
0
1
0
1
VALUE
VALUE
000000
—
—
—
—
—
—
—
—
—
—
—
Schottky diode present
Schottky diode open
Normal output current
Converter output current exceeded the current limit
Normal operation
Device temperature has exceeded thermal
shutdown threshold
Normal operation
V
Boost converter operating according to PWM
register and configuration register
Boost converter in standby mode
OUT
—
Boost-converter output PWM bit 1
Boost-converter output PWM bit 0 (LSB)
Boost-converter output PWM bit 9 (MSB)
Boost-converter output PWM bit 8
Boost-converter output PWM bit 7
Boost-converter output PWM bit 6
Boost-converter output PWM bit 5
Boost-converter output PWM bit 4
Boost-converter output PWM bit 3
Boost-converter output PWM bit 2
exceeded overvoltage limit
in a single register (0x20) to allow a single I
set the majority of the intensity level and minimize visible
flicker during intensity changes. The LSB register (0x21)
allows for very fine adjustments in LED intensity.
The MAX6948B checks the boost converter and indi-
cates its status in the boost-converter status register
(Table 6). Faults indicated in this register include ther-
mal shutdown, overvoltage, and current limit. The boost
converter goes into standby mode whenever the boost
standby bit (D0) = 1.
FUNCTION
FUNCTION
FUNCTION
Boost-Converter Status Register
DEFAULT VALUE
DEFAULT VALUE
DEFAULT VALUE
Read only
Read only
Read only
Read only
000000
000
2
0
0
0
0
0
0
0
0
0
0
1
C write to