IP1837TRPBF International Rectifier, IP1837TRPBF Datasheet - Page 24

• Manufacturer Part Number: IP1837TRPBF
• Description: IC DC-DC REG SYNC BUCK LGA
• Manufacturer: International Rectifier
• Series: iPOWIR™r
• Type: Step-Down (Buck), PWM - Voltage Moder

Specifications of IP1837TRPBF

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 V ~ 12 V
• Current - Output: 35A
• Frequency - Switching: 250kHz ~ 1.5MHz
• Voltage - Input: 1.5 V ~ 16 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: *
• Package / Case: *
• Package: LGA - 7.7 x 7.7
• Circuit: Single Output
• Iout (a): 35
• Switch Freq (khz): 250 - 1500
• Input Range (v): 1.5 - 16
• Output Range (v): 0.6 - 0.75*Vin
• Internal Bias Ldo: Yes
• Ocp Otp Uvlo Pre-bias Soft Start And: Remote Sense + Body Tracking + Temp Comp OCP
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

By replacing Z
function can be expressed as:
The compensation network has three poles and two zeros
and they are expressed as follows:
F
F
F
F
F
P
P
P
Z
Z
H(s) dB
H
1
1
2
3
2
(





s
)
0
2
2
2
2

Z




IN
Figure 19: Type III Compensation network
Gain(dB)

*
*
*
*
R
24
sR
R
R
R
C
C
in
1
10
1
3
and Z
10
3
8
7
7

 

(
F
*
and its asymptotic gain plot
( *
C
1
*
V
Z
C
C
C
1
1
4
OSO
C
March 3, 2011 | V1.24
4
R
4
4
1 (

R
f
R
7

8
*
according to Figure 19, the transfer
C

8
9

C
C
3
sR
F
)
Z
3
3
R




V
2
3
1
Fb
REF

 

10
C


)
4
sR
....
1 )


2
3


(25)

 

2
R
E/A
C

sC
C
F
*
3
4
P
4
R
*
7
2
1

*

3
C
R
C
C
1
C
*
7
8
3
3
3
C

*

 





F
3
R
R
1 (
C
P
10
Highly Integrated 35A Single‐input Voltage,
8
3
Comp

4


sR
Frequency
10
C
Z
(27)
(30)
(28)
Ve
(26)
(29)
f
7
)
Synchronous Buck Regulator
Cross over frequency is expressed as:
Based on the frequency of the zero generated by the
output capacitor and its ESR, relative to crossover
frequency, the compensation type can be different.
The table below shows the compensation types for
relative locations of the crossover frequency.
The higher the crossover frequency, the potentially faster
the load transient response will be. However, the
crossover frequency should be low enough to allow
attenuation of switching noise. Typically, the control loop
bandwidth or crossover frequency is selected such that:
The DC gain should be large enough to provide high
DC‐regulation accuracy. The phase margin should be
greater than 45
For this design we have:
It must be noted here that the value of the capacitance
used in the compensator design must be the small signal
value. For instance, the small signal capacitance of the
22uF capacitor used in this design is 12uF at 1.8V DC bias
and 600kHz frequency. It is this value that must be used for
all computations related to the compensation. The small
signal value may be obtained from the manufacturer’s
datasheets, design tools or SPICE models. Alternatively,
they may also be inferred from measuring the power stage
transfer function of the converter and measuring the
double pole frequency F
compute the small signal C
F
o
Compensator
V
V
β = V
Modulator gain = F
V
L
C

o
Type III
o
Type II
in
o
ref
R
Type
= 0.215uH
= 15x22uF, ESR = 3mOhm each
= 1.8V
= 12V
= 0.6V
3
ref
*
C
/V
7
o
=0.333
o
*
for overall stability.
V
in
F
*
o
F

LC

m
LC
< F
F
*

1/5
and using equation (16) to
LC
= 0.65, from Figure 15
F
F
o
ESR
ESR
< F
.
m
v/s F
~
< F
*
0
< F
1/10
2
0

< F
ESR
0
*
S

/2
L
*
1
o
F
*
s
iP1837
C
o
Electrolytic
Capacitor
Tantalum
Tantalum
Ceramic
Output
97600
(31)