参数资料
型号: LTC3444EDD#TRPBF
厂商: Linear Technology
文件页数: 17/20页
文件大小: 0K
描述: IC DC/DC CONV WCDMA 8-DFN
标准包装: 2,500
应用: 转换器,WCDMA 功率放大器应用
输入电压: 2.75 V ~ 5.5 V
输出数: 1
输出电压: 0.5 V ~ 5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 8-WFDFN 裸露焊盘
供应商设备封装: 8-DFN-EP(3x3)
包装: 带卷 (TR)
LTC3444
OPERATIO
However, due to the output voltage slewing requirements
found in WCDMA applications the output filter capacitor
C3
must be minimized. To maximize the transient response,
C2
R5
while minimizing the output capacitance, a higher band-
width, Type III compensation is required. A Type III
C1
R4
compensation network, refer to Figure 8, has a double zero
to cancel the double pole of the output LC filter and a
double pole to compensate for the ESR zero and RHP zero
of the boost topology. In addition to the double poles,
7
V C
FB
8
V REF
R2
R1
V OUT
the Type III network also has a single pole at DC. The
Type III compensation provides a maximum 135 ° phase
boost and allows the loop crossover to occur at frequen-
cies higher than the output LC. Refer to Figure 9. Referring
to Figure 8, the location of the poles and zeros are given by:
Assume C 2 >> C 3 , R 1 >> R 4 .
3444 F08
Figure 8, Error Amplifier with Type III Compensation
f POLE1 ?
1
2 ? π ? R 5 ? C 3
Hz
80
60
360
270
2 ? π ? R 4 ? C 1
f POLE2
=
1
Hz
40
20
0
f UO
180
90
0
2 ? π ? R 1 ? C 1
f ZERO1 =
1
Hz
–20
–40
–90
–180
f ZERO2
=
1
2 ? π ? R 5 ? C 2
Hz
–60
–80
1 e
1 e1
1 e2
1 e3
1 e4
1 e5 1 e6
1 e7
–270
–360
1 e8
FREQUENCY (Hz)
3444 G02
And the unity gain frequency (f UG ) of the Type III compen-
sation is given by:
Figure 9. Frequency Response for LTC3444 Error
Amplifier with a Typical Type III Compensation Network
f UG =
1
2 ? π ? R 1 ? C 2
Hz
where resistance is in ohms and capacitance is in farads.
Note: Bias resistor, R2, does not affect the Pole/Zero
placement.
3444fb
17
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