MAX6948B MAXIM [Maxim Integrated Products], MAX6948B Datasheet - Page 21

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

Converter and Five Constant-Current GPIO Ports
The active-low RST input operates as a reset that voids
any current I
forcing the device into the I
D6 bit in the configuration register (Table 2) to configure
RST to reset all the internal registers to the power-on-
reset state (Table 3). The RST input is overvoltage toler-
ant to 5.5V.
The MAX6948B ignores all I
remains low. The device uses this feature to minimize
supply current in power-critical applications by effective-
ly disconnecting the MAX6948B from the bus during idle
periods. RST also operates as a bus multiplexer, allow-
ing multiple devices to use the same I
Drive only one MAX6948B RST input high at any time to
use RST as a bus multiplexer.
The MAX6948B features a reset-run option. Taking the
RST input high brings the driver out of shutdown in addi-
tion to its normal function of enabling the device’s I
interface.
The MAX6948B features a reset-run option enabling RST
to bring the driver out of shutdown, in addition to its nor-
mal function of enabling the MAX6948B’s I
This provides an alternative method of bringing the driver
out of shutdown to writing to the configuration register
Figure 6. Output Fade DAC (Global Current = 0x07)
P2, P3, P4
CURRENT
10mA
5mA
0mA
P0, P1
CURRENT
30mA
15mA
0mA
PORT CURRENT = FULL
PORT CURRENT = HALF
CURRENT
FULL
High-Efficiency PWM LED Driver with Boost
RAMP-UP
2
C transaction involving the MAX6948B,
CURRENT
7/8
CURRENT
6/8
CURRENT
5/8
2
C STOP condition. Use the
2
C bus activity while RST
CURRENT
4/8
Reset-Run Option
CURRENT
3/8
2
C slave address.
RST Input
RAMP-DOWN
CURRENT
2/8
2
C interface.
CURRENT
1/8
ZERO
CURRENT
2
C
Figure 7. Global Current Modifies Ramp-Down Behavior
through the serial interface. The reset-run timing uses the
internal PWM clock.
After enabling the reset-run option, the MAX6948B uses
the rising edge on RST, followed by no I
ity to the MAX6948B for 128 to 129 periods of the GPIO
PWM clock (32kHz typ) to trigger the reset-run option.
If this timeout period elapses without the MAX6948B
acknowledging an I
run bit (D0) in the configuration register and brings itself
out of shutdown, activating any programmed ramp-up.
If RST pulses high for less than this timeout period to
trigger a reset run, the MAX6948B ignores the pulse and
continues to wait for a suitable trigger.
Cancel the reset-run trigger by transmitting an I
munication to the MAX6948B before the timeout period
elapses. The trigger cancels when the MAX6948B
acknowledges the I
ing at least the MAX6948B’s I
minimum timeout period is equal to 4ms. The minimum
I
and 8 data bits (9 bits total) within the minimum timeout
period is 9/4ms equal to 2.25kHz. Canceling the reset-
run trigger clears the reset-run bit (D1) in the configura-
tion register, disabling reset run. The run bit (D0) in the
configuration register remains cleared and the driver
remains in shutdown.
2
P2, P3, P4
CURRENT
C clock speed that guarantees a successful start bit
8.75mA
6.25mA
3.75mA
1.25mA
7.5mA
2.5mA
10mA
5mA
0mA
CURRENT
26.25mA
18.75mA
11.25mA
22.5mA
3.75mA
P0, P1
7.5mA
30mA
15mA
0mA
GLOBAL CURRENT = 0x07
GLOBAL CURRENT = 0x05
GLOBAL CURRENT = 0x03
GLOBAL CURRENT = 0x01
GLOBAL CURRENT = 0x00
GLOBAL CURRENT = 0x06
GLOBAL CURRENT = 0x04
GLOBAL CURRENT = 0x02
CURRENT
FULL
RAMP-UP
CURRENT
7/8
2
2
C transaction, the device sets the
C transaction and requires send-
CURRENT
6/8
CURRENT
5/8
2
CURRENT
C slave address. The
4/8
CURRENT
3/8
2
C interface activ-
CURRENT
RAMP-DOWN
2/8
CURRENT
2
1/8
C com-
ZERO
CURRENT
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