NCP3170AGEVB ON Semiconductor, NCP3170AGEVB Datasheet - Page 10

• Manufacturer Part Number: NCP3170AGEVB
• Description: BOARD EVALUATION NCP3170ADR2G
• Manufacturer: ON Semiconductor
• Series: -r

Specifications of NCP3170AGEVB

• Design Resources: NCP3170 Schematic NCP3170AGEVB BOM
• Main Purpose: DC/DC, Step Down
• Outputs And Type: 1, Non-Isolated
• Power - Output: -
• Voltage - Output: Adj down to 0.8V
• Current - Output: 3A
• Voltage - Input: 4.5 ~ 18 V
• Regulator Topology: Buck
• Frequency - Switching: 500kHz
• Board Type: Fully Populated
• Utilized Ic / Part: NCP3170
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: NCP3170AGEVBOS

with an integrated high−side PMOS switch and a low−side
NMOS switch. It operates from a 4.5 V to 18 V input voltage
range and supplies up to 3 A of load current. The duty ratio
can be adjusted from 8% to 92% allowing a wide output
voltage range. Features include enable control, Power−On
Reset (POR), input under voltage lockout, fixed internal soft
start, power good indication, over voltage protection, and
thermal shutdown.
Enable and Soft−Start
Figure 28 will force the part to disable below the minimum
input voltage of 4.13 V. The input under voltage disable
feature is used to prevent improper operation of the
converter due to insufficient voltages. The converter can be
turned on by tying the enable pin high and the part will
default to be input voltage enabled. The enable pin should
never be left floating.
threshold is required, the EN pin can be used. The trip
voltage of the EN pin comparator is 1.38 V typical. Upon
application of an input voltage greater than 4.41 V, the VIN
UVLO will release and the enable will be checked to
determine if switching can commence. Once the 1.38 V trip
voltage is crossed, the part will enable and the soft start
sequence will initiate. If large resistor values are used, the
EN pin should be bypassed with a 1 nF capacitor to prevent
coupling problems from the switch node.
The NCP3170 is a current−mode, step down regulator
An internal input voltage comparator not shown in
If an adjustable Under Voltage Lockout (UVLO)
Figure 29. Input Under Voltage Lockout Enable
C1
UV
4.5 V − 18 V
Figure 28. Input Voltage Enable
4.5 V − 18 V
C1
C1
IN
R1
R2
IN
UV
UV
EN
AGND
VIN
EN
AGND
VIN
NCP3170
NCP3170
DETAILED DESCRIPTION
http://onsemi.com
10
connecting a capacitor as shown in Figure 30.
threshold it can be added by use of a bias resistor to the
output. The hysteresis is created once soft start has initiated.
With the output voltage rising, current flows into the enable
node, raising the voltage. The thresholds for enable as well
as hysteresis can be calculated using Equation 1.
EN
VIN
R1
R2
R3
VOUT
The enable pin can be used to delay a turn on by
If the designer would like to add hysteresis to the enable
UV
UV
UV
VIN
TH
Figure 31. Added Hysteresis to the Enable UVLO
START
R3
VIN
Start
4.5 V − 18 V
UV
Rbias
C1
Vout
HYS
4.5 V − 18 V
DLY
+ EN
= Enable Threshold
= Input Voltage Start Threshold
= High Side Resistor
= Low Side Resistor
= Hysteresis Bias Resistor
= Regulated Output Voltage
+ VIN
C1
Figure 30. Delay Enable
IN
TH
C1
R1
R2
IN
Start
UV
UV
V
OUT
1 )
* EN
R3
EN
AGND
* EN
VIN
UV
R1
EN
AGND
TH
VIN
UV
TH
) R1
R2
*
UV
R2
EN
R2
NCP3170
UV
NCP3170
UV
UV
TH
R3
) R3
UV
UV
(eq. 1)