NCP1521BSNT1G ON Semiconductor, NCP1521BSNT1G Datasheet - Page 10

• Manufacturer Part Number: NCP1521BSNT1G
• Description: IC CONV DC-DC STEPDOWN SOT23-5
• Manufacturer: ON Semiconductor
• Type: Step-Down (Buck)r

Specifications of NCP1521BSNT1G

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.9 ~ 3.9 V
• Current - Output: 600mA
• Frequency - Switching: 1.5MHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: TSOT-23-5, TSOT-5, TSOP-5
• Mounting Style: SMD/SMT
• Duty Cycle (max): 100 %
• Efficiency: 90 %
• Input / Supply Voltage (max): 3.9 V
• Output Current: 600 mA
• Output Voltage: 3.3 V
• Switching Frequency: 1.5 MHz
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: NCP1521BSNT1GOSTR

Cycle−by−Cycle Current Limitation
is used to realize cycle−by−cycle current limit protection.
The comparator compares the LX pin voltage with the
reference voltage, which is biased by a constant current. If
the inductor current reaches the limit, the I
detects the LX voltage falling below the reference voltage
and releases the signal to turn off the switch Q1. The
cycle−by−cycle current limit is set at 1200 mA (nom).
Short Circuit Protection
the inductor current. The duty−cycle is minimum and the
consumption on the input line is 300 mA (Typ). When the
short circuit condition is removed, the device returns to the
normal mode of operation.
Soft−Start
inrush current when the device is initially enabled.
Soft−start is implemented by gradually increasing the
reference voltage until it reaches the full reference voltage.
During startup, a pulsed current source charges the internal
soft−start capacitor to provide gradually increasing
reference voltage. When the voltage across the capacitor
ramps up to the nominal reference voltage, the pulsed
current source will be switched off and the reference
voltage will switch to the regular reference voltage.
Shutdown Mode
the IC. In shutdown mode, the internal reference, oscillator
and most of the control circuitries are turned off. Therefore,
the typical current consumption will be 0.3 mA (typical
value). Applying a voltage above 1.2 V to EN pin will
enable the device for normal operation. The typical
threshold is around 0.7 V. The device will go through
soft−start to normal operation.
Thermal Shutdown
protect the integrated circuit in the event that the maximum
junction temperature is exceeded. If the junction
temperature exceeds 160°C, the device shuts down. In this
mode switch Q1 and Q2 and the control circuits are all
turned off. The device restarts in soft−start after the
temperature drops below 135°C. This feature is provided
to prevent catastrophic failures from accidental device
overheating, and it is not intended as a substitute for proper
heatsinking.
Low Dropout Operation
difference. The NCP1521B can operate at 100% duty
cycle. In this mode the PMOS (Q1) remains completely on.
From the block diagram (Figure 4), an I
When the output is shorted to ground, the device limits
The NCP1521B uses soft−start (300 ms Typ) to limit the
Forcing this pin to a voltage below 0.4 V will shut down
Internal Thermal Shutdown circuitry is provided to
The NCP1521B offers a low input to output voltage
LIM
LIM
comparator
comparator
http://onsemi.com
10
be calculated as:
•
•
•
•
USB or 5 V Rail Powered Applications
able to supply voltages up to 3.9 V, 600 mA, operating in
PWM mode only, with high efficiency (Figure 29), low
output voltage ripple and good load regulation results over
all current range (Figure 30).
−0.5
−1.0
−1.5
−2.0
The minimum input voltage to maintain regulation can
For USB or 5 V rail powered applications, NCP1521B is
100
V
I
R
R
2.0
1.5
1.0
0.5
90
80
70
60
50
OUT
V IN(min) + V OUT(max)
DS(on)
INDUCTOR
OUT
0
0
0
: Max Output Current
Figure 29. Efficiency vs. Output Current
: Output Voltage (Volts)
: P−Channel Switch R
100
100
: Inductor Resistance (DCR)
Figure 30. Load Regulation
) (I OUT
(V
(V
I
OUT
IN
IN
= 5.0 V, V
= 5.0 V, V
, OUTPUT CURRENT (mA)
200
200
(R DS(on) ) R INDUCTOR ))
I
OUT
300
OUT
OUT
300
, (mA)
DS(on)
= 3.9 V)
= 3.9 V)
400
400
25°C
25°C
500
500
−40°C
−40°C
85°C
85°C
(eq. 1)
600
600