ncp5810d ON Semiconductor, ncp5810d Datasheet - Page 10

• Manufacturer Part Number: ncp5810d
• Description: Dual 1 W Output Amoled Driver Supply
• Manufacturer: ON Semiconductor

addition, there are five functions which can reset the
flip-flop logic to switch off the MN1. The MAX DP
monitors the pulse width and if it exceeds 88% (nom) of the
cycle time the switch will be turned off. This limits the
switch from being on for more than one cycle. IPEAK
COMP compares the sensed inductor current with the
IPEAK_MAX threshold set at 700 mA (nom). If the current
exceeds this value, the controller turns off the NMOS
switch for the remainder of the cycle. This is a safety
function to prevent any excessive current that could
overload the inductor and the power stage. The boost
regulator is internally compensated and provides a
minimum of 45° phase margin.
Buck-Boost Inverter Operation
operation in Continuous Conduction Mode (CCM) in a
simplified way. During the first interval, the internal PMOS
power switch is turned on and the external Schottky diode
is reverse biased. The inductor stores energy through the
battery while the load is supplied by the output capacitor to
maintain regulation. During the second interval, the switch
is turned off and the diode is forward biased, this allows the
energy stored in the inductor to be supplied to both the load
and the capacitor.
converter can be expressed as:
to trigger the PWM controller on each rising edge (SET
signal) which starts a cycle. During this phase the high side
PMOS switch is turned on thus increasing the current
through the inductor. The switch current is measured by the
SENSE CURRENT and added to the RAMP COMP signal.
Then PWM COMPN compares the output of the adder and
the signal from ERROR AMP. When the comparator
threshold is exceeded, the PMOS power switch is turned off
until the rising edge of the next clock cycle. In addition,
there are five functions which can reset the flip-flop logic
to switch off the NMOS. The MAX DUTY CYCLE COMP
monitors the pulse width and if it exceeds 88% (nom) of the
cycle time the switch will be turned off. This limits the
switch from being on for more than one cycle. IPEAK
COMP compares the sensed inductor current with the
IPEAK_MAX threshold set at 800 mA (nom). If the current
exceeds this value, the controller turns off the PMOS
switch for the remainder of the cycle. This is a safety
function to prevent any excessive current that could
overload the inductor and the power stage.
Buck-Boost Compensation
compensated and provides a minimum of 45° phase
margin. But a 10 pF (C6) feed-forward capacitor is needed
to improved stability with C
Figure 9 depicts the two intervals of the buck-boost
In CCM, the voltage ratio of a buck-boost inverter
The internal oscillator provides a 1.75 MHz clock signal
Basically
V
OUT_N
V
the
IN
buck-boost
+
1 * D
D
OUTN
where D +
inverter
= 4.7 mF (C4) used to
T
T
ON
SW
is
internally
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NCP5810D
10
bypass VOUTN. Moreover in order to achieve excellent
the line transient rejection in critical conduction mode two
10 mF X5R in parallel for C
the feed-forward capacitor (C6) must be change from
10 pF to 68 pF as depicted Figure 16.
High Output Voltage Accuracy
reference (1% nom). Combined with the use of precision
feedback resistors, the NCP5810D will achieve highly
precise output voltages.
Excellent Line Transient Rejection and High Power
Supply Rejection Ratio
the NCP5810D the perfect solution for biasing Active
Matrix OLED displays. In order to have a steady, clean
display, OLEDs have to be biased by a very accurate
voltage with high immunity to line and load transients.
Both regulators have been specifically designed with high
loop gain and high phase margin to satisfy the great
constraints of AMOLED driving.
rejection ratio of 60 dB (nom).
PSRR is defined by
Out-of-Regulation Protection
feedback voltage protection. After soft-start sequence the
device is set to detect an out-of-regulation condition.
Under normal operation if the feedback voltage goes
beyond the nominal value by typically +/- 15% a fault is
detected. This fault could be caused by an overload, a
short-circuit or an open feedback condition. If this fault
remains for more than 1 ms, both converters shuts down to
protect device itself and any connected circuitry. The
NCP5810D remains in disable condition until reinitialized
by a rising edge on EN pin. Moreover to limit any
overvoltage during the power-up or the 1 ms delay caused
by and open feedback condition a small zener diode (D2)
is recommended as depicted Figure 17.
NCP5810D integrates a very accurate internal voltage
High output voltage accuracy and signal integrity makes
The boost converter features a high power supply
Both DC/DC regulators have implemented monitoring
0.1 μF
C5
VREF
5
Figure 16. Inverter Compensation
R2
FBN
* 20LOG
7
SWN
C6
R1
Feed-forward
10
OutputRipple
OUTN
L2
4.7 μH
VinRipple
* pF
D1
can be used. In this case
* μF
C4
C4
* μF
VOUTN