NCP1547DR2G ON Semiconductor, NCP1547DR2G Datasheet - Page 8

• Manufacturer Part Number: NCP1547DR2G
• Description: IC REG BUCK 1.5A 340KHZ 8-SOIC
• Manufacturer: ON Semiconductor
• Type: Step-Down (Buck)r

Specifications of NCP1547DR2G

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.5 ~ 24 V
• Current - Output: 1.5A
• Frequency - Switching: 340kHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

oscillation, as shown in Figure 8. Similar to current mode
control, this oscillation occurs at the duty cycle greater than
50% and can be alleviated by using a larger inductor value.
The current limit threshold is reduced to Foldback Current
when the FB pin falls below Foldback Threshold. This
feature protects the IC and external components under the
power up or over−load conditions.
BOOST Pin
power switch. A voltage higher than V
headroom to turn on the power switch. This in turn reduces
IC power dissipation and improves overall system
efficiency. The BOOST pin can be connected to an external
boost−strapping circuit which typically uses a 0.1 mF capacitor
and a 1N914 or 1N4148 diode, as shown in Figure 1.
BOOST pin is equal to
where:
voltage as well as the regulated output voltage (Figure 1).
However, the maximum voltage on the BOOST pin shall not
exceed 40 V.
constant 7.0 mA pre−driver current and base current
proportional to switch conducting current. A detailed
discussion of this current is conducted in Thermal
Consideration section. A 0.1 mF capacitor is usually
adequate for maintaining the Boost pin voltage during the on
time.
The BOOST pin provides base driving current for the
When the power switch is turned on, the voltage on the
V
The anode of the diode can be connected to any DC
As shown in Figure 9, the BOOST pin current includes a
F
= diode forward voltage.
Figure 8. The Regulator in Current Limit
V BOOST + V IN ) V O * V F
IN
provides required
http://onsemi.com
8
Shutdown
pin rises above the Startup Voltage. This ensures no
switching will occur until adequate supply voltage is
provided to the IC. Refer to Figure 10 for the SHDNB
(shutdown−bar) pin input circuit.
below the Shutdown Threshold Voltage. In sleep mode, the
power switch is kept open and the supply current reduces to
Shutdown Quiescent Current (1 mA typically). This pin has
an internal pull−down current. When not in use, pull this pin
up to V
resistor will ensure safe operation from below 9 V and
during a 40 V load dump condition.
The internal power switch will not turn on until the V
The IC enters a sleep mode when the SHDNB pin is pulled
30
25
15
10
20
5
0
Figure 9. The Boost Pin Current Includes 7.0 mA
Pre−Driver Current and Base Current when the
0
Switch is Turned On. The Beta Decline of the
CC
Power Switch Further Increases the Base
SHDNB
with a resistor (See Figure 1). A 100 kW pullup
Current at High Switching Current
SWITCHING CURRENT (A)
0.5
Figure 10.
V
20k
±33%
Z
1.2V
= 6V to 8V
1.0
-
+
GND
V
IN
1.5
IN