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| 型号： | LTC1148CS-3.3 |
| 厂商： | Linear Technology |
| 文件页数： | 14/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 14-SOIC |
| 标准包装： | 55 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 250kHz |
| 占空比： | 100% |
| 电源电压： | 3.5 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： | 0°C ~ 70°C |
| 封装/外壳： | 14-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
LTC1148
LTC1148-3.3/LTC1148-5
APPLICATIO S I FOR ATIO
With the addition of R3, a current is generated through R1
causing an offset of:
FROM CROWBAR DETECT CIRCUIT
(ACTIVE WHEN V GATE = V IN
5
VN2222LL
INTV CC
LTC1148
) )
V OFFSET = V OUT
R1
R1 + R3
OFF WHEN V GATE = GROUND) 4
C T
Figure 7. Output Crowbar Interface
LTC1148 ? F07
If V OFFSET > 25mV, the minimum threshold will be can-
R SENSE ≈ 75mV
celledandBurstModeoperationispreventedfromoccur-
ring. Since V OFFSET is constant, the maximum load current
is also decreased by the same offset. Thus, to get back to
the same I MAX , the value of the sense resistor must be
lower:
I MAX
To prevent noise spikes from erroneously tripping the
current comparator, a 1000pF capacitor is needed across
Pins 7 and 8.
Output Crowbar
An added feature to using an N-channel MOSFET as the
synchronous switch is the ability to crowbar the output
Troubleshooting Hints
Since efficiency is critical to LTC1148 series applications,
it is very important to verify that the circuit is functioning
correctly in both continuous and Burst Mode operation.
The waveform to monitor is the voltage on the timing
capacitor Pin 4.
In continuous mode (I LOAD > I BURST ) the voltage on the C T
pin should be a sawtooth with a 0.9V P-P swing. This
voltage should never dip below 2V as shown in Figure 8a.
When load currents are low (I LOAD < I BURST ) Burst Mode
operation should occur with the C T pin waveform periodi-
cally falling to ground as shown in Figure 8b.
3.3V
with the same MOSFET. Pulling the timing capacitor Pin
4 above 1.5V when the output voltage is greater than the
desired regulated value will turn “on” the N-channel
MOSFET.
A fault condition which causes the output voltage to go
above a maximum allowable value can be detected by
(a) CONTINUOUS MODE OPERATION
(b) Burst Mode OPERATION
0V
3.3V
0V
LTC1148 ? F08
external circuitry. Turning on the N-channel MOSFET
when this fault is detected will cause large currents to flow
and blow the system fuse.
The N-channel MOSFET needs to be sized so it will safely
handle this overcurrent condition. The typical delay from
pulling the C T pin high and the N drive Pin 14 going high
Figure 8. C T Waveforms
If Pin 4 is observed falling to ground at high output
currents, it indicates poor decoupling or improper ground-
ing. Refer to the Board Layout Checklist.
is 250ns. Note: Under shutdown conditions, the N-chan-
nel is held OFF and pulling the C T pin high will not cause
the N-channel MOSFET to crowbar the output.
A simple N-channel FET can be used as an interface
between the overvoltage detect circuitry and the LTC1148
as shown in Figure 7.
114835fd
14
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| LTC1148CS5 | 制造商:LT 功能描述:HOUSE MARKED |
| LTC1148CS-5 | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1148CS-5#PBF | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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 |
| LTC1148CS-5#TR | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
| LTC1148CS-5#TRPBF | 功能描述:IC REG CTRLR BUCK PWM CM 14-SOIC 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:4,500 系列:PowerWise® PWM 型:控制器 输出数:1 频率 - 最大:1MHz 占空比:95% 电源电压:2.8 V ~ 5.5 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 ~ 125°C 封装/外壳:6-WDFN 裸露焊盘 包装:带卷 (TR) 配用:LM1771EVAL-ND - BOARD EVALUATION LM1771 其它名称:LM1771SSDX |
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