- 您现在的位置：买卖IC网 > PDF目录15273 > LTC3802EGN#TR (Linear Technology)IC REG CTRLR BUCK PWM VM 28-SSOP PDF资料下载
参数资料
| 型号： | LTC3802EGN#TR |
| 厂商： | Linear Technology |
| 文件页数： | 19/28页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 28-SSOP |
| 标准包装： | 2,500 |
| 系列： | PolyPhase® |
| PWM 型： | 电压模式 |
| 输出数： | 2 |
| 频率 - 最大： | 850kHz |
| 占空比： | 92% |
| 电源电压： | 3 V ~ 30 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： | 28-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
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页当前第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
LTC3802
APPLICATIO S I FOR ATIO
As the output load current decreases in continuous mode,
the average current in the inductor will reach a point where
it drops below half the ripple current. At this point, the
current in the inductor will reverse during a portion of the
switching cycle, or begin to flow from the output back to
the input. This does not adversely affect regulation, but
does cause additional losses as a portion of the inductor
To minimize the switching loss and reverse current flow at
light loads, the LTC3802 switches to a second mode of
operation: Burst Mode operation (Figure 5b). In Burst
Mode operation, at the end of the QB cycle, if the inductor
current approaches zero or goes negative, the LTC3802
turns off both drivers. The actual cutoff threshold is
proportional to the I MAX setting and is equal to:
current flows back and forth through the resistive power
switches, giving away a little more power each time and
lowering the efficiency. There are some benefits to allow-
–
V IMAX
100
– 3 mV
ing this reverse current flow: the circuit will maintain
regulation even if the load current drops to zero and the
output ripple voltage and frequency remain constant at all
loads, easing filtering requirements. However, continuous
mode at low output current does cause losses in effi-
ciency. A portion of the inductor current flows back and
forth through the resistive power switches, causing I 2 R
losses. The drivers continue to switch QT and QB on and
off once a cycle. Each time an external MOSFET is turned
on, the internal driver must charge its gate to a potential
above the MOSFET’s source voltage; when the MOSFET is
turned off, that charge is lost to ground or SW. At the high
switching frequencies, the lost gate charges can add up to
tens of millicoulombs. As the load current continues to
drop, these charges quickly become the dominant power
loss term, reducing efficiency once again.
I AVERAGE
I RIPPLE
The –3mV built-in offset overcomes the random mis-
match in the burst compararator trip point and allows
Burst Mode operation at no load.
Once both MOSFETs shut off, the voltage at the SW pin will
float around V OUT , and the inductor current and the voltage
across the inductor will be close to zero. This prevents
current from flowing backwards in QB, eliminating that
power loss term.
The moment the LTC3802 enters Burst Mode operation,
both drivers skip a number of switching cycles until the
internal 36 μ s timeout forces the switcher to return to
continuous operation. This timeout eliminates the audible
noise from certain types of inductors when they are lightly
loaded. After the 36 μ s timeout, the LTC3802 forces one
continuous mode cycle and checks the inductor current at
the end of the period. If it is still too small, it enters Burst
Mode operation again. This pattern repeats until the out-
put is loaded. The LTC3802 returns to continuous mode
operation if it detects that CMPIN potential is 12mV below
or 15mV above its nominal bandgap voltage. Immediately
after returning to continuous mode operation, the regula-
tor output might continue to droop slightly until the feed-
TIME
Figure 5a. Continuous Mode
I RIPPLE
3802 F05a
back loop responds and requests an increase in duty cycle.
During sudden transient steps, the regulator output ripple
is limited by the feedback loop transient response and is
independent of the mode of operation.
The small 15mV and –12mV offset at the POS and NEG
RESET comparators ensure that after a transient load step,
the LTC3802 returns to continuous mode quickly. This
minimizes the output ripple under Burst Mode operation.
TIME
Figure 5b. Burst Mode Operation
3802 F05b
I AVERAGE
For proper Burst Mode operation, the LTC3802 requires
very precise CMPIN and FB sensing. To realize this,
CMPIN and FB must use the same resistive divider values
3802f
19
相关PDF资料 |
PDF描述 |
|---|---|
| VI-J5K-EW-F4 | CONVERTER MOD DC/DC 40V 100W |
| H2BXG-10108-L4-ND | JUMPER-H1501TR/A2015L/X 8" |
| VI-J5K-EW-F3 | CONVERTER MOD DC/DC 40V 100W |
| LTC3731HG#TRPBF | IC REG CTRLR BUCK PWM CM 36-SSOP |
| VI-J5K-EW-F2 | CONVERTER MOD DC/DC 40V 100W |
相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC3802EUH | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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 |
| LTC3802EUH#PBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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 |
| LTC3802EUH#TR | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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 |
| LTC3802EUH#TRPBF | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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 |
| LTC3803ES6 | 制造商:Linear Technology 功能描述:DC DC Cntrlr Single-OUT Flyback Controller 9.2V to 75V Input 6-Pin TSOT-23 |
发布紧急采购，3分钟左右您将得到回复。