NCP3065PG ON Semiconductor, NCP3065PG Datasheet - Page 8

• Manufacturer Part Number: NCP3065PG
• Description: IC LED DRIVR HP CONST CURR 8-DIP
• Manufacturer: ON Semiconductor
• Type: High Power, Constant Currentr

Specifications of NCP3065PG

• Constant Current: Yes
• Topology: PWM, Step-Down (Buck), Step-Up (Boost)
• Number Of Outputs: 1
• Internal Driver: Yes
• Type - Primary: Automotive
• Type - Secondary: High Brightness LED (HBLED)
• Frequency: 250kHz
• Voltage - Supply: 3 V ~ 40 V
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Operating Temperature: -40°C ~ 125°C
• Current - Output / Channel: 1.5A
• Internal Switch(s): Yes
• Output Current: 1.5 A
• Input Voltage: 3 V to 40 V
• Switching Frequency: 250 KHz
• Mounting Style: Through Hole
• Current, Input Bias: -100 nA
• Current, Supply: 7 mA
• Frequency, Oscillator: 150 kHz
• Package Type: PDIP-8
• Regulator Type: Switching
• Temperature, Operating, Range: -40 to +125 °C
• Voltage, Supply: 0 to 40 V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Output: -
• Efficiency: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: NCP3065PGOS

Peak Current Sense Comparator
initiated by the Voltage Feedback comparator and
terminated by the oscillator. Abnormal operating conditions
occur when the converter output is overloaded or when
feedback voltage sensing is lost. Under these conditions, the
I
output Switch. The switch current is converted to a voltage
by inserting a fractional ohm resistor, R
V
across R
If the voltage drop exceeds 200 mV (nom) with respect to
V
output switch conduction on a cycle−by−cycle basis. This
Comparator/Latch configuration ensures that the Output
Switch has only a single on−time during a given oscillator
cycle.
specified at static conditions. In dynamic operation the
sensed current turn−off value depends on comparator
response time and di/dt current slope.
The di/dt current slope is dependent on the voltage
difference across the inductor and the value of the inductor.
Increasing the value of the inductor will reduce the di/dt
slope.
application at worst conditions to be sure that the max peak
current will never get over the 1.5 A Darlington Switch
Current max rating.
Thermal Shutdown
the IC in the event that the maximum junction temperature
is exceeded. When activated, typically at 165°C, the
Darlington Output Switch is disabled. The temperature
sensing circuit is designed with some hysteresis. The
Darlington Switch is enabled again when the chip
temperature decreases under the low threshold. This feature
is provided to prevent catastrophic failures from accidental
device overheating. It is not intended to be used as a
replacement for proper heatsinking.
R
pk
V
CC
CC
V
s
Under normal conditions, the output switch conduction is
The V
Real V
Typical I
It is recommended to verify the actual peak current in the
Internal thermal shutdown circuitry is provided to protect
turn−off
ipk(sense)
Resistor
Current Sense comparator will protect the Darlington
, the comparator will set the latch and terminate the
V turn_off + V ipk(sense) ) Rsc @ (t_delay @ di dt)
and the Darlington output switch. The voltage drop
Real
on
SC
IPK(Sense)
turn−off
pk
is monitored by the Current Sense comparator.
comparator response time t_delay is 350 ns.
on R
Current Limit Sense Voltage threshold is
Io
di/dt slope
sc
resistor
t_delay
I1
SC
, in series with
I through the
Darlington
Switch
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8
LED Dimming
dimming capability. In digital input mode the PWM input
signal inhibits switching of the regulator and reduces the
average current through the LEDs. In analog input mode a
PWM input signal is RC filtered and the resulting voltage is
summed with the feedback voltage thus reduces the average
current through the LEDs. Figure 15 illustrated the linearity
of the digital dimming function with a 200 Hz digital PWM.
For further information on dimming control refer to
application note AND8298.
No Output Capacitor Operation
focuses on the control of the current through the load, not the
voltage across it. The switching frequency of the NCP3065
is in the range of 100−250 kHz which is much higher than
the human eye can detect. This allows us to relax the ripple
current specification to allow higher peak to peak values.
This is achieved by configuring the NCP3065 in a
continuous conduction buck configuration with low peak to
peak ripple thus eliminating the need for an output filter
capacitor. The important design parameter is to keep the
peak current below the maximum current rating of the LED.
Using 15% peak to peak ripple results in a good compromise
between achieving max average output current without
exceeding the maximum limit. This saves space and reduces
part count for applications that require a compact footprint.
(Example: See Figure 17) See application note AND8298
for more information.
Output Switch
configuration. This allows the application designer to
operate at all conditions at high switching speed and low
voltage drop. The Darlington Output Switch is designed to
switch a maximum of 40 V collector to emitter voltage and
current up to 1.5 A.
The COMP pin of the NCP3065 is used to provide
A constant current buck regulator such as the NCP3065
The output switch is designed in a Darlington
800
700
600
500
400
300
200
100
0
0
10
20
30
DUTY CYCLE (%)
Figure 15.
40
50
24 V
24 V
60
in
in
, V
, V
12 V
f
70
= 3.6 V
f
= 7.2 V
in
, V
80
f
= 3.6 V
90
100