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参数资料
| 型号： | LTC3823EUH#PBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 32-QFN |
| 标准包装： | 73 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 占空比： | 90% |
| 电源电压： | 4.5 V ~ 36 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 32-WFQFN 裸露焊盘 |
| 包装： | 管件 |
LTC3823
APPLICATIONS INFORMATION
V OUT 2 ( MIN ) = 0 . 6 V ? 1 +
?
on, the switch node rises to V IN and the BOOST pin rises
to approximately V IN + INTV CC . The boost capacitor needs
to store about 100 times the gate charge required by the
top MOSFET. In most applications 0.1μF to 0.47μF, X5R
or X7R dielectric capacitor is adequate.
Discontinuous Mode Operation and FCB Pin
The FCB pin determines whether the bottom MOSFET
remains on when current reverses in the inductor. Tying
this pin above its 0.6V threshold enables discontinuous
operation where the bottom MOSFET turns off when in-
ductor current reverses. The load current at which current
reverses and discontinuous operation begins depends on
the amplitude of the inductor ripple current and will vary
with changes in V IN . Tying the FCB pin below the 0.6V
threshold forces continuous synchronous operation, al-
lowing current to reverse at light loads and maintaining
high frequency operation. To prevent forcing current back
of the transformer. However, if the controller goes into
discontinuous mode and halts switching due to a light
primary load current, then V OUT2 will droop. An external
resistor divider from V OUT2 to the FCB pin sets a minimum
voltage V OUT2(MIN) below which continuous operation is
forced until V OUT2 has risen above its minimum.
? R 4 ?
? R 3 ?
Fault Conditions: Current Limit and Foldback
The maximum inductor current is inherently limited in a
current mode controller by the maximum sense voltage.
In the LTC3823, the maximum sense voltage is controlled
by the voltage on the V RNG pin. With valley current control,
the maximum sense voltage and the sense resistance
determine the maximum allowed inductor valley current.
The corresponding output current limit is:
+ Δ I L
intothemainpowersupply,potentiallyboostingtheinput
supply to a dangerous voltage level, forced continuous
mode of operation is disabled when the TRACK/SS volt-
I LIMIT =
V SNS ( MAX )
R DS ( ON ) ρ T
1
2
age is 20% below the reference voltage during soft-start
or tracking up. Forced continuous mode of operation is
also disabled when the TRACK/SS voltage is below 0.1V
during tracking down operation. During these two periods,
the PGOOD signal is forced low.
In addition to providing a logic input to forced continu-
ous operation, the FCB pin provides a mean to maintain
a ?yback winding output when the primary is operating
in discontinuous mode. The secondary output V OUT2 is
normally set as shown in Figure 5 by the turns ratio N
The current limit value should be checked to ensure that
I LIMIT(MIN) > I OUT(MAX) . The minimum value of current limit
generally occurs with the largest V IN at the highest ambi-
ent temperature, conditions that cause the largest power
loss in the converter. Note that it is important to check for
self-consistency between the assumed MOSFET junction
temperature and the resulting value of I LIMIT which heats
the MOSFET switches.
Caution should be used when setting the current limit
based upon the R DS(ON) of the MOSFETs. The maximum
current limit is determined by the minimum MOSFET
LTC3823
V IN
TG
+
V IN
C IN
1N4148
+
V OUT2
C OUT2
1μF
on-resistance. Data sheets typically specify nominal
and maximum values for R DS(ON) , but not a minimum.
A reasonable assumption is that the minimum R DS(ON)
lies the same percentage below the typical value as the
maximum lies above it. Consult the MOSFET manufacturer
R4
R3
FCB
SW
BG
T1
1:N
?
+
V OUT1
C OUT
for further guidelines.
To further limit current in the event of a short circuit to
ground, the LTC3823 includes foldback current limiting.
SGND
PGND
3823 F05
If the output falls by more than 60%, then the maximum
sense voltage is progressively lowered to about one tenth
Figure 5. Secondary Output Loop
of its full value.
3823fd
15
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相关代理商/技术参数 |
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|---|---|
| LTC3823IGN#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,000 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:1MHz 占空比:50% 电源电压:9 V ~ 10 V 降压:无 升压:是 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 85°C 封装/外壳:8-TSSOP（0.173"，4.40mm 宽） 包装:带卷 (TR) |
| LTC3823IGN#PBF | 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN DC/DC CTRL SSOP-28 |
| LTC3823IGN#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 28-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:96% 电源电压:4 V ~ 36 V 降压:无 升压:是 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-40°C ~ 125°C 封装/外壳:24-WQFN 裸露焊盘 包装:带卷 (TR) |
| LTC3823IUH#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 32-QFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 特色产品:LM3753/54 Scalable 2-Phase Synchronous Buck Controllers 标准包装:1 系列:PowerWise® PWM 型:电压模式 输出数:1 频率 - 最大:1MHz 占空比:81% 电源电压:4.5 V ~ 18 V 降压:是 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:无 工作温度:-5°C ~ 125°C 封装/外壳:32-WFQFN 裸露焊盘 包装:Digi-Reel® 产品目录页面:1303 (CN2011-ZH PDF) 其它名称:LM3754SQDKR |
| LTC3823IUH#PBF | 制造商:Linear Technology 功能描述:IC SYNC STEP-DOWN DC/DC CONTROLLER QFN32 |
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