NCP1587DR2G ON Semiconductor, NCP1587DR2G Datasheet - Page 11

• Manufacturer Part Number: NCP1587DR2G
• Description: IC CTLR SYNC BUCK LV 8-SOIC
• Manufacturer: ON Semiconductor
• Type: Step-Down (Buck)r

Specifications of NCP1587DR2G

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: Adjustable
• Current - Output: 1A
• Frequency - Switching: 275kHz
• Voltage - Input: 4.5 ~ 13.2 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Topology: Boost, Buck
• Output Voltage: 0.8 V to 5 V
• Output Current: 8 mA
• Switching Frequency: 300 KHz
• Duty Cycle (max): 80 %
• Operating Supply Voltage: 15 V
• Supply Current: 8 mA
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: 0 C
• Mounting Style: SMD/SMT
• Synchronous Pin: No
• Number Of Pwm Outputs: 2
• On/off Pin: Yes
• Adjustable Output: Yes
• Switching Freq: 300KHz
• Duty Cycle: 80%
• Operating Supply Voltage (max): 13.2V
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC N
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

DESIGN EXAMPLE II: Type III Compensation
(Oscon Cap. with small ESR; Do not place R
Choose the loop gain crossover frequency;
The corner frequency of the output filter is calculated below;
Check the ESR zero frequency;
Choose C
gain magnitude, one zero position and the soft start. By
adjusting the value of this compensation capacitor, the
crossover frequency and the soft start time can be adjusted.
Zeros of the compensation network are calculated as follows;
Switching Frequency
Output Capacitance
Output Capacitance
Output Inductance
Input Voltage
Output Voltage
The compensation capacitor (C
1st zero;
F
F
F
LC
ESR
ESR
C1
+
for the soft start
+
+
2
2
2
F
co
p
+ 1
p
p
C
5
C1
1 mH
R
7 mW
1
1
ESR
+ 33 nF
F
1
sw
Figure 13. Closed-loop Voltage Loop-gain of the NCP1587
+ 55 KHz
1120 mF
C
C1
560 mF
O
F
R
C
L
V
V
) is related to the loop
sw
ESR
out
out
out
in
= 12 V
= 275 KHz
= 1 mH
= 1.6 V
= 2×560 mF
+ 4.7 KHz
+ 40.6 KHz
= 7 mW/Each
C
, C
C
http://onsemi.com
, C
P
)
11
Blue curve: Gain-Frequency
Red curve: Gain-Frequency
(Phase margin = 61.417 degree, Gain margin = 9.347 dB)
stable system with transconductance amplifier. Ù choose
R
much larger than 2/gm for the stable system.
Poles of the compensation network are calculated as follows;
C1
R
2nd zero;
Choose R3 for the crossover frequency. R3 should be
Choose C20 = 3.3 nF
1st pole;
Choose R4 to cancel the output capacitor ESR zero.
C1
= 12.1 kW
should be much larger than 2/gm in order to get the
R3 + 10 kW
F
C20 +
R4 +
R
z2
C1
+
+ F
+
+
+
2
2
2
2
F
LC
2
2
P1
F
p
p
Z1
+ 4.7 KHz
+ F
p
p
p
p
+
F
40.6 kHz
1
1
ESR
F
F
4.7 KHz
P1
10
F
1
470 Hz
LC
z2
1
z1
1
+ 40.6 KHz
1
+ 470 Hz
C20
R3
C
C1
3.3 n
10 kW
30 nF
+ 1.2 kW
+ 11.3 kW
+ 3.4 nF