SP6134HV Datasheet, PDF (12/14 Pages) Sipex Corporation – Dual Supply Synchronous Buck 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 SP6134CU 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
1.2
1.2
1.5
1.9
Capacitance
(uF)
22
47
INDUCTORS - SURFACE MOUNT
Inductor Specification
Manufacturer/Part No.
Series R
mΩ
I_SAT
Size
(a) LxW(mm) Ht.(mm)
Inductor Type
Manufaturer
Website
Easy Magnet SC5018-2R7M 4.30
TDK RLF 12560T-2R7N110 4.50
Coilcraft DO5010P-332HC
8.60
12.0 12.6x12.6
12.2 12.5x12.8
17.0 14.7x15.2
4.5 Shielded Ferrite Core inter-technical.com
6.0 Shielded Ferrite Core tdk.com
8.0 Unshielded Ferrite Core coilcraft.com
Easy Magnet SC5018-1R2M 1.96
Inter-Technical SC4015-1R2M 4.37
Coilcraft DO5010P-152HC
4.00
TDK RLF 12560T-1R9N120 3.60
20.0 12.6x12.6
17.0 10.0x10.0
25.0 14.7x15.2
13.2 12.5x12.8
4.5 Shielded Ferrite Core inter-technical.com
3.8 Shielded Ferrite Core inter-technical.com
8.0 Unshielded Ferrite Core coilcraft.com
6.0 Shielded Ferrite Core tdk.com
CAPACITORS -SURFACE MOUNT
Manufacturer/Part No.
ESR Ripple Current
Size
Voltage Capacitor
Ω (max) (A)@45°C LxW(mm) Ht.(mm) (V)
Type
Manufaturer
Website
TDK C3225X5R1C226M 0.002
4.00
3.2x2.5 2.0
16.0 X5R Ceramic tdk.com
TDK C3225X5ROJ476M 0.002
4.00
3.2x2.5 2.5
6.3 X5R Ceramic tdk.com
MOSFET - Surface Mount
MOSFET Manufacturer/Part No.
RDS (on)
Ω (max)
ID Current Qg
Qg Voltage Foot Print
(A)
nC(Typ) nC(Max) (V)
N-Channel Fairchild Semi FDS6676S 0.006
14.50
43
60.0
30.0 SO-8
N-Channel Fairchild Semi FD7088N3 0.005
21.10
37
48.0
30.0 SO-8
N-Channel Vishay Si4336DY
0.004
25.0
32
50.0
30.0 SO-8
Note: Components highlighted in Bold are those used on the SP6134H Evaluation Board.
Table 1. Input and Output Stage Components Selection Charts.
Manufaturer
Website
fairchildsemi.com
fairchildsemi.com
vishay.com
Rev: C Date: 2/3/04
SP6134H Dual Supply, Synchronous Buck Controller
12
© Copyright 2004 Sipex Corporation