SP6132 Datasheet, PDF (11/14 Pages) Sipex Corporation – Wide Input, 300KHz Synchronous PWM Controller

APPLICATIONS INFORMATION: Continued
The goal of loop compensation is to manipulate
loop frequency response such that its gain crosses
over 0db at a slope of -20db/dec. The first step
of compensation design is to pick the loop
crossover frequency. High crossover frequency
is desirable for fast transient response, but often
jeopardizes the system stability. Crossover fre-
quency should be higher than the ESR zero but
less than 1/5 of the switching frequency. The
ESR zero is contributed by the ESR associated
with the output capacitors and can be deter-
mined by:
When the output capacitors are of a Ceramic
Type, the SP6132CU Evaluation Board requires
a Type III compensation circuit to give a phase
boost of 180° in order to counteract the effects of
an under damped resonance of the output filter
at the double pole frequency.
Gain
(dB)
Condition:
C22 >> CP1, R1 >> RZ3
Error Amplify Gain
Bandwidth Product
ƒ_Z(ESR) =
1
2π C_OUT R_ESR
The next step is to calculated the complex con-
jugate poles contributed by the LC output filter,
ƒ_P(LC) =
1
2π L C_OUT
20 Log (RZ2/R1)
Frequency
(Hz)
Bode Plot of Type III Error Amplify Compensation.
Inductance
(uH)
2.7
2.7
3.3
Manufacturer/Part No.
Easy Magnet SC5018-2R7M
TDK RLF12560T-2R7N110
Coilcraft DO5010P-332HC
1.2
Easy Magnet SC5018-1R2M
1.2
Inter-Technical SC4015-1R2M
1.5
Coilcraft DO5010P-152HC
1.9
TDK RLF12560T-1R9N120
Capacitance(u
F)
22
47
Manufacturer/Part No.
TDK C3225X5R1C226M
TDK C3225X5R0J476M
MOSFET
N-Channel
N-Channel
Manufacturer/Part No.
Fairchild Semi FDS7088N3
Vishay Si4336DY
Series R
mOhms
4.30
4.50
8.60
INDUCTORS - SURFACE MOUNT
Inductor Specification
Isat
Size
Inductor Type
(A)
LxW(mm) Ht.(mm)
12.0
12.6x12.6 4.5 Shielded Ferrite Core
12.2
12.5x12.8 6.0 Shielded Ferrite Core
17.0
14.7x15.2
8.0 Unshielded Ferrite Core
1.96
4.37
20.0
17.0
12.6x12.6
10.0x10.0
4.5 Shielded Ferrite Core
3.8 Shielded Ferrite Core
4.00
3.60
25.0
13.2
14.7x15.2
12.5x12.8
8.0 Unshielded Ferrite Core
6.0 Shielded Ferrite Core
CAPACITORS - SURFACE MOUNT
ESR
Capacitor Specification
Ripple Current
Size
Voltage
Capacitor
ohms (max)
0.002
(A) @ 45C
4.00
LxW(mm) Ht.(mm) (V)
3.2x2.5
2.0
16.0
Type
X5R Ceramic
0.002
4.00
3.2x2.5
2.5
6.3 X5R Ceramic
MOSFETS - SURFACE MOUNT
RDS(on)
ohms (max)
0.005
MOSFET Specification
ID Current
Qg
Voltage
(A)
nC (Typ) nC (Max) (V)
21.0
37.0
48.0 30.0
Foot Print
SO-8
0.004
25.0
32.0
50.0 30.0
SO-8
Manufacturer
Website
www.easymagnet.com
www.tdk.com
www.coilcraft.com
www.easymagnet.com
www.inter-technical.com
www.coilcraft.com
www.tdk.com
Manufacturer
Website
www.tdk.com
www.tdk.com
Manufacturer
Website
www.fairchildsemi.com
www.Vishay.com
Note: Components highlighted in bold are those used on the SP6132 Evaluation Board.
Table 1. Input and Output Stage Components Selection Charts.
Date: 8/4/04
SP6132 Wide Input, 300KHz Synchronous PWM Controller
11
© Copyright 2004 Sipex Corporation