NCP1840Q8A6MNG ON Semiconductor, NCP1840Q8A6MNG Datasheet - Page 15

• Manufacturer Part Number: NCP1840Q8A6MNG
• Description: LED Lighting Drivers PRGRM MULTI LED DRIVER
• Manufacturer: ON Semiconductor

Specifications of NCP1840Q8A6MNG

• Product Category: LED Lighting Drivers
• Rohs: yes
• Input Voltage: 3 V to 5.5 V
• Operating Frequency: 400 kHz
• Maximum Supply Current: 0.75 mA
• Output Current: 30 mA
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Package / Case: QFN-20
• Minimum Operating Temperature: - 40 C

Soft Start−Up
circuitry that is used to provide soft start−up. As the supply
voltage is applied, the POR will sense when the voltage
reaches a level that will allow all circuitry to operate
correctly. It then will gradually apply this supply voltage to
the chip to minimize noise and reduce EMI. If during
operation the supply voltage drops, the POR will ensure that
the part is reset before the voltage reaches a level where the
circuitry won’t operate as intended. This helps to mitigate
strange operation during a power glitch or brown−out
situation.
Low Power Mode
into low power mode about 5 ms after all LED outputs are
turned OFF and there is no I
Objective: To set the currents for each LED, except LED8, to 1.5 mA. LED8 will be set to 3.0 mA. All LEDs will have
a 50% PWM duty cycle. After these registers are loaded, then only LEDs 1, 2, 3, 4, and 8 will be activated. Later,
LED8 will be turned off. Lastly the PWM register value for LED1 will be read. Note that R
example.
Step 1. Set the current level for ALL LEDs to 1.5 mA.
Step 2. Set the current level for LED8 to 3.0 mA.
Step 3. Set the PWM duty cycle for all LEDs to 50%.
1.1 Set the Part Address to 1B (hex).
1.2 Set the Read/Write bit to 0.
1.3 Set the Control Bits to 011 to program all Current Level Registers at the same time.
1.4 Set the Data to 05 (hex), which will set the current to 1.5 mA.
2.1 Set the Part Address to 1B (hex).
2.2 Set the Read/Write bit to 0.
2.3 Set the Control Bits to 001 and set the Register address to 07 (hex) to write to LED8 Current Level Register.
2.4 Set the Data to 0B (hex), which will set the current to 3.0 mA.
3.1 Set the Part Address to 1B (hex).
3.2 Set the Read/Write bit to 0.
3.3 Set the Control Bits to 100 to program all PWM Registers at the same time.
3.4 Set the Data to 20 (hex), which will set the PWM duty cycle to 50%.
The NCP1840 has an on−chip power−on−reset (POR)
All registers are reset to all zeros on start−up.
The NCP1840 minimizes power consumption by entering
Start
Start
Start
S
S
S
Part Address
Part Address
Part Address
0011011
0011011
0011011
R/W
R/W
R/W
2
0
0
0
C communication. During low
Ack
Ack
Ack
A
A
A
Control
Control
Control
011
001
100
Bits
Bits
Bits
http://onsemi.com
EXAMPLE
Register Address
Register Address
Register Address
Don’t Care
Don’t Care
15
00111
power mode, the I
settings are retained, but the charge pump and other circuitry
that is not needed is powered down. Bit D2 of the Main
Status Register is set to a logic one during low power mode.
The part is brought out of this mode when the Master
initiates communication with it via the I
this happens, the part returns to normal operation and bit D2
is set to a logic zero. Therefore, when the Master wakes up
the device, it can read bit D2 and wait for this bit to change
to 0, indicating that all circuitry is back to full operation. The
transition period from when the part receives the wake−up
to full normal operation takes less than 1 ms.
Unused LED Channels
tied to the charge pump output to ensure that these channels
remain OFF and to save power consumption that would
otherwise be lost.
Any of the 8 LED channels that are not needed should be
Ack
Ack
Ack
A
A
A
2
C interface is still active and all register
Register Data
Register Data
Register Data
00000101
00001011
00100000
BIAS
= 10.25 kW for this
2
C interface. When
Ack
Ack
Ack
A
A
A
Stop
Stop
Stop
P
P
P