- 您现在的位置：买卖IC网 > PDF目录15248 > LTC1876EG (Linear Technology)IC REG CTRLR BST PWM CM 36-SSOP PDF资料下载
参数资料
| 型号： | LTC1876EG |
| 厂商： | Linear Technology |
| 文件页数： | 23/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST PWM CM 36-SSOP |
| 标准包装： | 37 |
| 系列： | PolyPhase® |
| PWM 型： | 电流模式 |
| 输出数： | 3 |
| 频率 - 最大： | 360kHz |
| 占空比： | 99.4% |
| 电源电压： | 3.5 V ~ 36 V |
| 降压： | 是 |
| 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 ~ 85°C |
| 封装/外壳： | 36-SSOP（0.209"，5.30mm 宽） |
| 包装： | 管件 |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页当前第23页第24页第25页第26页第27页第28页第29页第30页第31页第32页第33页第34页第35页第36页
LTC1876
APPLICATIO S I FOR ATIO
approximately 220kHz. The FREQSET pin can be grounded
to lower this frequency to approximately 140kHz or tied to
the INTV CC pin to yield approximately 310kHz. The FREQSET
pin may be driven with a voltage from 0 to INTV CC to fix or
modulate the oscillator frequency as shown in Figure 5.
Minimum On-Time Considerations
Minimum on-time t ON(MIN) is the smallest time duration
that the step down controller is capable of turning on the
top MOSFET. It is determined by internal timing delays and
the gate charge required to turn on the top MOSFET. Low
duty cycle applications may approach this minimum on-
time limit and care should be taken to ensure that.
synchronous switch duty factor. Thus, the FCB input pin
removes the requirement that power must be drawn from
the inductor primary in order to extract power from the
auxiliary windings. With the loop in continuous mode, the
auxiliary outputs may nominally be loaded without regard
to the primary output load.
The secondary output voltage V SEC is normally set as
shown in Figure 6a by the turns ratio N of the transformer:
V SEC ? (N + 1) V OUT
However, if the controller goes into Burst Mode operation
and halts switching due to a light primary load current,
then V SEC will droop. An external resistive divider from
V SEC to the FCB pin sets a minimum voltage V SEC(MIN) :
t ON ( MIN ) <
V SEC ( MIN ) ≈ 0 . 8 V ? 1 +
R 5 ?
V OUT
V IN ( f )
If the duty cycle falls below what can be accommodated by
?
?
R 6 ?
?
the minimum on-time, the controller will begin to skip
cycles. The output voltage will continue to be regulated,
but the ripple voltage and current will increase.
The minimum on-time for each controller is generally less
than 200ns. However, as the peak sense voltage decreases
the minimum on-time gradually increases up to about
300ns. This is of particular concern in forced continuous
applications with low ripple current at light loads. If the
duty cycle drops below the minimum on-time limit in this
situation, a significant amount of cycle skipping can occur
with correspondingly larger current and voltage ripple.
If V SEC drops below this level, the FCB voltage forces
temporary continuous switching operation until V SEC is
again above its minimum.
In order to prevent erratic operation if no external connec-
tions are made to the FCB pin, the FCB pin has a 0.18 μ A
internal current source pulling the pin high. Include this
current when choosing resistor values R5 and R6.
The following table summarizes the possible states avail-
able on the FCB pin:
Table 1
FCB Pin
Condition
FCB Pin Operation
The FCB pin can be used to regulate a secondary winding
or as a logic level input. Continuous operation is forced
when the FCB pin drops below 0.8V. During continuous
mode, current flows continuously in the transformer pri-
mary. The secondary winding(s) draw current only when
the bottom, synchronous switch is on. When primary load
0V to 0.75V
0.85V < V FB < 4.3V
Feedback Resistors
>4.8V
Forced Continuous (Current Reversal
Allowed—Burst Inhibited)
Minimum Peak Current Induces
Burst Mode Operation
No Current Reversal Allowed
Regulating a Secondary Winding
Burst Mode Operation Disabled
Constant Frequency Mode Enabled
currents are low and/or the V IN /V OUT ratio is low, the
synchronous switch may not be on for a sufficient amount
of time to transfer power from the output capacitor to the
secondary load. Forced continuous operation will support
secondary windings providing there is sufficient
No Current Reversal Allowed
No Minimum Peak Current
Remember that both controllers are temporarily forced
into continuous mode when the FCB pin falls below 0.8V.
1876fa
23
相关PDF资料 |
PDF描述 |
|---|---|
| LTC1876EG#PBF | IC REG CTRLR BST PWM CM 36-SSOP |
| CAT809MTBI-T3 | IC VOLTAGE SUPERVISOR SOT-23-3 |
| ELL-3GM3R9N | COIL PWR CHOKE 3.9UH 940MA SMD |
| CAT809JTBI-T3 | IC VOLTAGE SUPERVISOR SOT-23-3 |
| ELL-3GM3R3N | COIL PWR CHOKE 3.3UH 980MA SMD |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1876EG#PBF | 功能描述:IC REG CTRLR BST PWM CM 36-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC1876EG#TR | 功能描述:IC REG CTRLR BST PWM CM 36-SSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC1876EG#TRPBF | 功能描述:IC REG CTRLR BST PWM CM 36-SSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:PolyPhase® 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 |
| LTC1877EMS8 | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V，1.5V，1.8V，2.5V 输入电压:2.7 V ~ 20 V PWM 型:- 频率 - 开关:- 电流 - 输出:50mA 同步整流器:是 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:10-TFSOP，10-MSOP（0.118"，3.00mm 宽）裸露焊盘 包装:带卷 (TR) 供应商设备封装:10-MSOP 裸露焊盘 |
| LTC1877EMS8#PBF | 功能描述:IC REG BUCK SYNC ADJ 0.6A 8MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 标准包装:250 系列:- 类型:降压（降压） 输出类型:固定 输出数:1 输出电压:1.2V 输入电压:2.05 V ~ 6 V PWM 型:电压模式 频率 - 开关:2MHz 电流 - 输出:500mA 同步整流器:是 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:6-UFDFN 包装:带卷 (TR) 供应商设备封装:6-SON（1.45x1） 产品目录页面:1032 (CN2011-ZH PDF) 其它名称:296-25628-2 |
发布紧急采购，3分钟左右您将得到回复。