ncp5890 ON Semiconductor, ncp5890 Datasheet - Page 7

• Manufacturer Part Number: ncp5890
• Description: Light Management Ic Dedicated For Lcd Backlighting And Multi-led Fun Light Applications
• Manufacturer: ON Semiconductor

DC/DC OPERATION
generate the output voltage necessary to drive the series
arranged LED. The system includes an open load detection
to avoid over voltage situation when the LED are
disconnected from the Vout pin. A built−in circuit prevent
high inrush current when the system is powered.
mirror controlled by the digital content of the ILEDREG
register. With a typical 1.3 Mhz operation frequency, the
converter can run at full power with a tiny 4.7 mH inductor.
However, care must be observed, at ESR level, to optimize
the total DC/DC conversion efficiency. In particular, the
ferrite material shall have limited eddy current losses at
high frequency. Depending upon the type of material, the
eddy losses in the inductor can range from a low 40 mW to
a high 250 mW under the same bias and load conditions.
current mirror connected to the FB pin. The voltage at this
pin can vary between a low 100 mV to a 1.5 V maximum,
depending upon the ILED current amplitude. Typically, the
FB voltage will be 425 mV under normal operation.
I2C Protocol
from the MCU to the NCP5890. Leaving aside the
Acknowledge bit, the NCP5890 chip does not return data
back to the MCU.
Table 1. Recommended Inductor Manufacturers
LPQ3310−472
The boost converter is based on a PWM structure to
The ILED is regulated by means of a built−in current
The ILED current is regulated by the means of internal
The standard I2C protocol is used to transfer the data
Part Number
COILCRAFT
TDK
MURATA
Manufacturers
Figure 5. Typical Switching Operation
http://onsemi.com
7
0111 001X or 0111 010X (the X being the Read / Write
identifier as defined by the I2C specification) depending
upon the digital status present at the I2CADR pin:
The physical address of the NCP5890 can be selected as
Vbat
Figure 4. Simplified Boost Structure
FEEDBACK
Current Sense
+
−
H1
Vbat
H
2
V
ILED = 25 mA
M8
bat
Vbat
= 3.6 V
2
4.7uH
1
L1
3
1
Iref
I1
DNSR0320MW2T1
M9
3
1
D5
470 nF
2
2
C1
3
1
M10
D6
D2
D3
D4