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參數(shù)資料
| 型號： | MAX1802 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Digital Camera Step-Down Power Supply |
| 中文描述： | 數(shù)碼相機降壓型電源 |
| 文件頁數(shù)： | 24/28頁 |
| 文件大?。?/td> | 469K |
| 代理商： | MAX1802 |
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M
Digital Camera Step-Down
Power Supply
24
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3) Place the compensation zero at the same frequency
as the maximum output pole frequency (in Hz):
Solving for CC:
Use values of C
C
<10nF. If the above calculation deter-
mines that the capacitor should be >10nF, use C
C
=
10nF, skip step 4, and go to step 5.
4) Determine the crossover frequency (in Hz):
and to maintain at least 10dB gain margin, make sure
that the crossover frequency is
≤
1/3 of the ESR zero
frequency, or 3f
C
≤
Z
O
, or ESR
≤
D / 6 V
REF
.
If this is not the case, go to step 5 to reduce the error-
amplifier high-frequency gain to decrease the
crossover frequency.
5) The high-frequency gain may be reduced, thus
reducing the crossover frequency, as long as the
zero due to the compensation network remains at or
below the crossover frequency. In this case:
and
Choose C
OUT
, R
C
, and C
C
to satisfy both equations
simultaneously.
Continuous Inductor Current
For continuous inductor current, there are two condi-
tions that change, requiring different compensation.
The response of the control loop includes a right-half-
plane zero and a complex pole pair due to the inductor
and output capacitor. For stable operation, the con-
troller-loop gain must drop below unity (0dB) at a much
lower frequency than the right-half-plane zero frequen-
cy. The zero arising from the ESR of the output capaci-
tor is typically used to compensate the control circuit
by increasing the phase near the crossover frequency,
increasing the phase margin. If a low-value, low-ESR
output capacitor (such as a ceramic capacitor) is used,
the ESR-related zero occurs at too high a frequency
and does not increase the phase margin. In this case,
use a lower value inductor so that it operates with dis-
continuous current (see the
Discontinuous Inductor
Current
section).
For continuous inductor current, the gain of the voltage
divider is A
VDV
= V
REF
/ V
OUT,
and the DC gain of the
error amplifier is A
VEA
= 2000. The gain through the
PWM controller in continuous current is:
Thus, the total DC loop gain is: A
VDC
= 2000 V
OUT
/ V
IN
.
The complex pole pair due to the inductor and output
capacitor occurs at the frequency (in Hz):
The pole and zero due to the compensation network at
COMP occur at the frequencies (in Hz):
G
C
C
4000
π
Z
1
2 R C
C
C
=
P
C
C
EA
C
=
(
)
=
1
4 10
7
π
P
V
V
LC
O
OUT
IN
OUT
=
2
π
A
VO
OUT
V V
V
=
2
f
C
D
C
REF
=
≥
G
R C
EA C
π
OUT
C
π
1
2
ESR
D
G
EA C
≤
V
REF
6
f
V
C
C
REF
OUT
=π
D
C
C
OUT OUT
R I
C
OUT
V
(
IN
OUT
IN
V
2V
(
V
=
)
)
Z
R C
V
C
C
OUT
LOAD MIN
R
OUT
C
OUT
IN
V
IN
2V
V
2
=
=
(
1
2
π
π
(
)
FREQUENCY
A
VDC
GAIN
(dB)
PHASE
180
°
90
°
0
°
O
-20
20
40
60
80
PHASE
Z
C
= P
O
Z
0
P
C
GAIN
Figure 7. Discontinuous-Current, Voltage-Mode, Step-Up
Controller Bode Plot
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| MAX1802EHJ | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| MAX1802EHJ+ | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| MAX1802EHJ+T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
| MAX1802EHJ-T | 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 Step-Up Slave DC/DC Controller RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風格:SMD/SMT |
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