NCP3063 ONSEMI [ON Semiconductor], NCP3063 Datasheet - Page 8

• Manufacturer Part Number: NCP3063
• Description: 1.5 A, Step−Up/Down/Inverting Switching Regulators
• Manufacturer: ONSEMI [ON Semiconductor]

Peak Current Sense Comparator
normal conditions, output switch conduction is 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
comparator will protect the Darlington output Switch. The
switch current is converted to a voltage by inserting a
fractional ohm resistor, R
Darlington output switch. The voltage drop across R
monitored by the Current Sense comparator. If the voltage
drop exceeds 200 mV with respect to V
will set the latch and terminate output switch conduction on
a
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.
of the NCP3063. Three main converter topologies are
demonstrated with actual test data shown below each of the
circuit diagrams.
Rs Resistor
V
V
With a voltage ripple gated converter operating under
turn−off
The V
Figures 14 through 22 show the simplicity and flexibility
ipk(sense)
cycle−by−cycle
Real
on
IPK(Sense)
Current Limit Sense Voltage threshold is
Io
di/dt slope
basis.
SC
t_delay
, in series with V
This
I1
Comparator/Latch
CC
NCP3063, NCP3063B, NCV3063
, the comparator
pk
Current Sense
I through the
CC
Darlington
and the
Switch
http://onsemi.com
APPLICATIONS
SC
is
8
The di/dt current slope is growing with voltage difference on
the inductor pins and with decreasing inductor value.
the 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 160°C, the Output
Switch is disabled. The temperature sensing circuit is
designed with 10°C hysteresis. The Switch is enabled again
when the chip temperature decreases to at least 150°C
threshold. This feature is provided to prevent
catastrophic
overheating. It is not intended to be used as a
replacement for proper heatsinking.
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.
parameters. Additionally, a complete application design aid
for the NCP3063 can be found at www.onsemi.com.
Real V
Typical I
It is recommended to check the real max peak current in
Internal thermal shutdown circuitry is provided to protect
The output switch is designed in a Darlington
Figure 13 gives the relevant design equations for the key
V turn_off + V ipk(sense) ) Rs @ (t_delay @ di dt)
turn−off
pk
comparator response time t_delay is 350 ns.
on Rsc resistor
failures
from
accidental
device