NCP5608 ON Semiconductor, NCP5608 Datasheet - Page 7

• Manufacturer Part Number: NCP5608
• Description: Multiple LED Charge Pump Driver
• Manufacturer: ON Semiconductor

DC−DC OPERATION
generate a DC voltage capable to supply the white LED
load. The system regulates the current flowing into each
LED by means of internal current mirrors associated with
the white diodes. Consequently, the output voltage will be
equal to the Vf of the LED, plus the 300 mV (typical)
developed across the internal NMOS mirror. Typically,
assuming a standard white LED forward biased at 10 mA,
the output voltage will be 3.2 V.
extra mode of operation, with a significant efficiency
improvement of the converter over the normal battery
voltage span. The threshold levels have been defined to
optimize this range of operating voltages, assuming a high
efficiency is not relevant when the system is connected to
a battery charger (i.e. Vbat > 4.5 V).
output and stops the converter when the voltage is above
The converter is based on a charge pump technique to
The third external capacitor makes possible the 1.33X
The built−in OVP circuit continuously monitors each
C1N
Q1
Q2
PIN 16
GND
2.90 V − 4.10 V
Li−Ion
C1
CURRENT CONTROL
C1P
Q3
Q4
PIN 17
GND
Figure 3. Basic DC−DC NCP5608 Converter Structure
Q5
APPLICATIONS INFORMATION
C2N
Q6
PIN 20
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NCP5608
PIN 19
C2
7
GND
5.0 V. The converter resumes normal operation when the
voltage drops below 5.0 V (no latch−up mechanism).
Consequently, the chip can operate with no load during any
test procedures, but in the case of special applications, it is
recommended to connect the unused LED driver either to
the V
accommodate the modes selected by the analog functions.
regulated according to the value defined by the
programming message. The total current is limited to
500 mA DC.
C2P
The structure is built with power MOS devices to
The current flowing into each LED is continuously
The system runs with two cycles:
Q8
Q7
PIN 21
− Cycle#1
− Cycle#2
OUT
supply to avoid any uncontrolled operation.
Fly capacitors are charged from the battery.
Energy accumulated into the fly capacitors is
transferred to the load.
LEDx
Q9
PWRGND
PIN 13
C3N
Q10
PIN 23
PIN 18
V
OUT
C3
C3P
Q12
Q11
PIN 22