lt3471edd-trpbf Linear Technology Corporation, lt3471edd-trpbf Datasheet - Page 10

• Manufacturer Part Number: lt3471edd-trpbf
• Description: Dual 1.3a, 1.2mhz Boost/inverter In 3mm ? 3mm Dfn
• Manufacturer: Linear Technology Corporation

LT3471
APPLICATIONS
The Current Mode zero is a right half plane zero which can
be an issue in feedback control design, but is manageable
with proper external component selection.
Using the circuit of Figure 2 as an example, Table 3 shows
the parameters used to generate the Bode plot shown in
Figure 7.
10
R
V
C
C
C
C
C
C
g
g
R
R
R
R1, R2: FEEDBACK RESISTOR DIVIDER NETWORK
R
C
ma
mp
C
OUT
PL
C
L
O
ESR
: COMPENSATION CAPACITOR
: OUTPUT RESISTANCE DEFINED AS V
: COMPENSATION RESISTOR
: OUTPUT RESISTANCE OF g
: PHASE LEAD CAPACITOR
: TRANSCONDUCTANCE AMPLIFIER INSIDE IC
: POWER STAGE TRANSCONDUCTANCE AMPLIFIER
R
Figure 6. Boost Converter Equivalent Model
: OUTPUT CAPACITOR
: OUTPUT CAPACITOR ESR
O
–
+
g
mp
g
U
ma
+
–
INFORMATION
U
ma
REFERENCE
1.00V
OUT
C
PL
DIVIDED BY I
W
Figure 7. Bode Plot of 3.3V to 7V Application
–10
–20
–30
3471 F06
70
60
50
40
30
20
10
R1
R2
0
100
LOAD(MAX)
R
ESR
C
OUT
U
GAIN
PHASE
R
1k
L
V
OUT
FREQUENCY (Hz)
10k
Table 3. Bode Plot Parameters
From Figure 7, the phase is –115° when the gain reaches
0dB giving a phase margin of 65°. This is more than
adequate. The crossover frequency is 50kHz.
Parameter
100k
C
R
V
g
g
C
V
R
R
C
R
R1
R2
OUT
ESR
OUT
f
ma
mp
L
PL
IN
S
O
C
L
C
3471 F07
1M
0
–50
–100
–150
–200
–250
–300
–350
–400
Value
90.9
4.7
0.9
3.3
9.3
2.2
1.2
20
10
90
33
55
15
50
7
µmho
Units
mho
MHz
mΩ
MΩ
kΩ
kΩ
kΩ
µH
µF
pF
pF
Ω
V
V
Comment
Application Specific
Application Specific
Application Specific
Not Adjustable
Not Adjustable
Adjustable
Not Adjustable
Adjustable
Adjustable
Application Specific
Application Specific
Not Adjustable
Not Adjustable
Application Specific
Not Adjustable
3471fa