NCP5810 ON Semiconductor, NCP5810 Datasheet - Page 10

• Manufacturer Part Number: NCP5810
• 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. The buck−boost
inverter is internally compensated and provides a
minimum of 45° phase margin.
Sequencing
output first comes up, and then the negative output does.
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
The sequencing is designed internally. The positive
V
OUT_N
V
IN
+
1 * D
D
where D +
T
T
SW
ON
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NCP5810
10
High Output Voltage Accuracy
reference (1% nom). Combined with the use of precision
feedback resistors, the NCP5810 will achieve highly
precise output voltages.
Excellent Line Transient Rejection and High Power
Supply Rejection Ratio
the NCP5810 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
Enable
converter. An active high logic level on this pin enables the
device. A built−in pull−down resistor disables the device if
the pin is left open.
True Shut Down
and truly isolates the battery from the output. The True shut
down eliminates the leakage current from the battery to the
load and significantly reduces battery consumption during
disable condition, thus increasing battery life.
Inrush Current Limiting Circuitry
unknown whether the output capacitor COUTP is charged
or discharged. If the output capacitor is discharged, a
common boost converter shows high inductor inrush
current at start−up. The internal circuitry of the NCP5810
has been carefully designed to limit the amplitude of the
inrush current at start−up.
Thermal Shutdown
the power section of the device is disabled. Normal
operation will resume when the junction temperature drops
below 150°C (nom).
Design Procedure
Buck−Boost Inverter Output Voltage Setting
adjusted using external feedback resistors, and can be set
from −2 V down to −15 V. Unlike for the boost converter,
the lower feedback resistor R2 does not use the ground as
a reference but uses the reference voltage (nom 1.265 V).
NCP5810 integrates a very accurate internal voltage
High output voltage accuracy and signal integrity makes
The boost converter features a high power supply
This input logic allows enabling and disabling the
When in disable condition, the switch MP0 is turned off
Before the NCP5810 boost converter is turned on, it is
When the IC junction temperature exceeds 165°C (nom),
The output voltage of the buck−boost inverter is also
* 20LOG
OutputRipple
VinRipple