ncp5810c ON Semiconductor, ncp5810c Datasheet - Page 11

• Manufacturer Part Number: ncp5810c
• Description: Dual 1 W Output Amoled Driver Supply
• Manufacturer: ON Semiconductor

R2 is placed between the feedback pin FBN (nom 632 mV)
and the reference pin REF. As for the boost converter, the
current flowing out of the feedback resistors must be as low
as possible to ensure high efficiency in low load conditions.
Nevertheless the feedback resistor impedance must not be
too high to keep good voltage accuracy. Therefore it is
recommended to use values in the 10 kW to 100 kW range
for the lower resistor R2. The upper feedback resistor R1
can calculated using the following equation:
56 kW ±1% is selected of R2, R1 should be selected
according to the following equation:
Inductor Selection
considered when selecting an inductor, the absolute value
of the inductor, the saturation current and the DCR. During
normal operation, the NCP5810C is intended to operate in
Continuous Conduction Mode (CCM). The two equations
below can be used to calculate the peak current for each
converters:
For the boost converter
For the buck-boost inverter
current, L the inductor value, F the switching frequency,
and D
current. A good approximation is to use h = 0.8 from the
boost and h = 0.75 for the buck-boost inverter. It is
important to ensure that the inductor current rating is high
enough such that it not saturate. As the inductor size is
reduced, the peak current for a given set of conditions
increases along with higher current ripple so it is not
possible to deliver maximum output power at lower
inductor values. Finally an acceptable DCR must be
selected regarding losses in the coil and must be lower than
300 mW to limit excessive voltage drop. In addition, as
DCR is reduced, overall efficiency will improve. The
inductor value should range between 2.7 mH and 6.8 mH,
typically for each DC/DC converter, it is recommended to
For example, should one need –5.4 V for V
Three different electrical parameters need to be
Where V
The global converter efficiency h varies with load
X
R
the duty cycle.
1
I
I
PEAK_N
PEAK_P
+ 56
IN
R
But : V
So: R
is the battery voltage, I
1
+
+
+ R
h
h
1
1 ) 2
FBN
I
N
P
OUT_N
+ R
2
I
OUT_P
+
(1 * D
(1 * D
1.265
2
V
V
V
OUTN
REF
5.4
2
FBN
D
1 )
N
P
N
)
)
* V
+ 536 kW "1%
* V
)
)
2
2
2
REF
V
V
FBN
OUT_X
V
IN
IN
V
REF
L
L
OUTN
P
N
D
D
P
N
is the load
F
OUTN
F
http://onsemi.com
, if a
NCP5810C
11
use a 4.7 mH low profile inductor. Some recommended
inductors include but are not limited to:
TDK: VLF3010AT-4R7MR70 (1.0 mm)
TDK: MLP3216S2R7T (0.6 mm)
SUMIDA: CDH2D09BNP (1.0 mm)
MARUWA CXFU0208-4R7 (0.8 mm)
Schottky Diode Selection
negative output. The reverse voltage rating of the selected
diode must be equal to or greater than the difference
between the output voltage of the inverter and the input
voltage. The average current rating of the diode must be
greater than the maximum output load current. The peak
current rating must be larger than the maximum peak
inductor current. It is recommended to use a Schottky diode
with lower forward voltage to minimize the power
dissipation and therefore to maximize the efficiency of the
converter.
capacitance versus reverse voltage and leakage current
versus junction diode temperature. Both parameters are
impacting the efficiency in low load condition and
switching quiescent current.
limited to:
ON SEMICONDUCTOR: NSR0320MW2
ON SEMICONDUCTOR: RB521S30
ROHM: RSX051VA-30
PHILIPS: PMEG2005AEL
Input and Output Capacitors
and sustain the load during the T
minimize the output ripple, a 4.7 mF low ESR multi-layer
ceramic capacitor type X5R is recommended. To achieve
high performances (signal integrity) one 4.7 mF 6.3 V X5R
should be used to bypass the power input supply C
(PVIN) and one 1.0 mF 6.3 V X5R should be used to bypass
the analog input supply C
effects in ceramic capacitor. Actually smaller the case-size
and higher the DC bias voltage, the bigger drop in
capacitance. For a stability viewpoint the percentage drop
in capacitance for the chosen input or output operating
voltage must be limit to 20%.
limited to:
4.7 mF 6.3 V 0603
4.7 mF 10 V 0805
An external diode is required for the rectification of the
Also a particular care must be observed for parasitic
Some recommended Schottky diodes include but are not
C
Also a particular care must be observed for DC-bias
Some recommended capacitors include but are not
TDK: C1608X5R0J475MT
TDK: CGB4B1X5R0J475M (0.5 mm)
TDK: C2012X5R1A475MT
MURATA: GRM219R61A475KE
OUTP
and C
OUTN
store energy during the T
INA
(AVIN).
ON
phase. In order to
OFF
phase
INP