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参数资料
| 型号： | LTC3822EMSE#TRPBF |
| 厂商： | Linear Technology |
| 文件页数： | 15/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-MSOP |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 850kHz |
| 占空比： | 99% |
| 电源电压： | 2.75 V ~ 4.5 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 |
| 包装： | 带卷 (TR) |
LTC3822
APPLICATIONS INFORMATION
pin waveforms that will give a sense of the overall loop
stability. The gain of the loop will be increased by increas-
ing R C and the bandwidth of the loop will be increased
by decreasing C C . The output voltage settling behavior is
related to the stability of the closed-loop system and will
demonstrate the actual overall supply performance. For
a detailed explanation of optimizing the compensation
components, including a review of control loop theory,
refer to Application Note 76.
A second, more severe transient is caused by switching
in loads with large (>1μF) supply bypass capacitors. The
discharged bypass capacitors are effectively put in parallel
with C OUT , causing a rapid drop in V OUT . No regulator can
deliver enough current to prevent this problem if the load
switch resistance is low and it is driven quickly. The only
solution is to limit the rise time of the switch drive so that
the load rise time is limited to approximately (25) ? (C LOAD ).
Thus a 10μF capacitor would be require a 250μs rise time,
limiting the charging current to about 200mA.
Design Example
For a design example, V IN will be a 3.3V power supply.
Output voltage is 1.2V with a load current requirement of
10A. The I PRG and FREQ pins will be left ?oating, so the
maximum current sense threshold Δ V SENSE(MAX) will be
approximately 120mV and the switching frequency will
be 550kHz.
A 22A 0.39μH inductor works well for this application.
C IN will require an RMS current rating of at least 5A
at temperature. A C OUT with 25mΩ ESR will cause ap-
proximately 100mV output ripple. Figure 7 shows a 12A,
3.3V IN /1.8V OUT application.
PC Board Layout Checklist
When laying out the printed circuit board, use the follow-
ing checklist to ensure proper operation of the LTC3822.
Figure 5 shows a suggested PCB ?oorplan.
? The power loop (input capacitor, MOSFET, inductor, output
capacitor) and high di/dt loop (V IN , through both MOSFETs
to power GND and back through C IN to V IN ) should be as
small as possible and located on one layer. Excess induc-
tance here can cause increased stress on the MOSFETs
and increased high frequency ringing on the output.
? Put the feedback resistors close to the V FB pins. The I TH
compensation components should also be very close
to the LTC3822. All small-signal circuitry should be iso-
lated from the main switching loop with ground Kelvin
connected to the output capacitor ground.
? The current sense traces (V IN and SW) should be Kelvin
connected right at the top-side MOSFET source and
drain. The positive current sense pin is shared with
the V IN pin. This must not be locally decoupled with a
capacitor.
Duty Cycle =
V OUT
V IN
= 36.4%
? Keep the switch node (SW) and the gate driver nodes
(TG, BG) away from the small-signal components, es-
From Figure 1, SF = 96%.
pecially the feedback resistors, and I TH compensation
components.
R DS(ON)MAX =
5
6
? 0.9 ? SF ?
Δ V SENSE(MAX)
I OUT(MAX) ? ρ T
= 0.011 Ω
? Place CB as close as possible to the SW and BOOST
pins. This capacitor carries high di/dt MOSFET gate
drive currents. The charging current to the boost diode
The Si4486DY has an R DS(ON) of 9mΩ. To prevent induc-
tor saturation during a short circuit, the inductor current
rating should be higher than 20A.
For 4A I RIPPLE , the required minimum inductor value is:
should be provided from a separate V IN trace than that
to the V IN pin.
? Beware of ground loops in multiple layer PC boards. Try
to maintain one central signal ground node on the board.
? ? 1 –
? = 0.35μH
L MIN =
1.2V ?
550kHz ? 4A ?
1.2V ?
3.3V ?
If the ground plane must be used for high DC currents,
keep that path away from small signal components.
3822fa
15
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| LTC3823EGN#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:2,500 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) |
| LTC3823EGN#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) |
| LTC3823EUH#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:- 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) |
| LTC3823EUH#TRPBF | 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:- 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) |
| 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) |
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