NCP1529ASNT1GEVB ON Semiconductor, NCP1529ASNT1GEVB Datasheet - Page 11

• Manufacturer Part Number: NCP1529ASNT1GEVB
• Description: BOARD EVAL NCP1529
• Manufacturer: ON Semiconductor

Specifications of NCP1529ASNT1GEVB

• Design Resources: NCP1529ASNT1GEVB Schematic NCP1529ASNT1GEVB Gerber Files NCP1529ASNT1GEVB Bill of Materials
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Soft−Start
when the device is initially powered up or 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.
Cycle−by−cycle Current Limitation
realize cycle−by−cycle current limit protection. The
comparator compares the SW pin voltage with the reference
voltage, which is biased by a constant current. If the inductor
current reaches the limit, the I
SW 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 1600 mA (nom).
Low Dropout Operation
difference. The NCP1529 can operate at 100% duty cycle.
minimum input voltage to maintain regulation can be
calculated as:
•
•
•
•
Undervoltage Lockout
NCP1529 enables the DC/DC converter output to begin the
start up sequence (see soft−start section). The UVLO
threshold hysteresis is typically 100 mV.
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 DC/DC converter for normal operation. 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
V
The NCP1529 uses soft−start to limit the inrush current
From the block diagram, an I
The NCP1529 offers a low input to output voltage
In this mode the PMOS (Q1) remains completely ON. The
The Input voltage V
Forcing this pin to a voltage below 0.4 V will shut down
Internal Thermal Shutdown circuitry is provided to
V
I
R
R
out
OUT
DS(on)
INDUCTOR
OUT
+ V
: Max Output Current
: Output Voltage (V)
: P−Channel Switch R
OUT(max)
: Inductor Resistance (DCR)
) I
IN
OUT
must reach 2.4 V (typ) before the
R
DS(on)
LIM
DS(on)
LIM
_R
comparator detects the
comparator is used to
INDUCTOR
(eq. 1)
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11
temperature exceeds 180°C, the device shuts down. In this
mode all power transistors and control circuits are turned
off. The device restarts in soft−start after the temperature
drops below 140°C. This feature is provided to prevent
catastrophic failures from accidental device overheating.
Short Circuit Protection
inductor current. The duty−cycle is minimum and the
consumption on the input line is 550 mA (typ). When the
short circuit condition is removed, the device returns to the
normal mode of operation.
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 28), low
output voltage ripple and good load regulation results over
all current range (Figure 29).
100
When the output is shorted to ground, the device limits the
For USB or 5 V rail powered applications, NCP1529 is
−0.5
−1.0
−1.5
−2.0
−2.5
−3.0
95
90
85
80
75
70
65
60
55
50
45
40
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
0
Figure 29. Load Regulation vs. Output Current
Figure 28. Efficiency vs. Output Current
200
200
I
I
OUT
(V
OUT
(V
IN
, OUTPUT CURRENT (mA)
IN
, OUTPUT CURRENT (mA)
= 5.0 V, V
= 5.0 V, V
400
400
25°C
25°C
OUT
OUT
600
600
= 3.9 V)
= 3.9 V)
85°C
85°C
800
800
−40°C
−40°C
1000
1000