参数资料
型号: LTC3830-1ES8#TRPBF
厂商: Linear Technology
文件页数: 11/24页
文件大小: 0K
描述: IC REG CTRLR BUCK PWM VM 8-SOIC
标准包装: 2,500
PWM 型: 电压模式
输出数: 1
频率 - 最大: 250kHz
占空比: 95%
电源电压: 3 V ~ 8 V
降压:
升压:
回扫:
反相:
倍增器:
除法器:
Cuk:
隔离:
工作温度: -40°C ~ 85°C
封装/外壳: 8-SOIC(0.154",3.90mm 宽)
包装: 带卷 (TR)
LTC3830/LTC3830-1
APPLICATIO S I FOR ATIO
External Clock Synchronization
The LTC3830 SHDN pin doubles as an external clock input
for applications that require a synchronized clock. An
internal circuit forces the LTC3830 into external synchro-
nization mode if a negative transition at the SHDN pin is
detected. In this mode, every negative transition on the
SHDN pin resets the internal oscillator and pulls the ramp
signal low, this forces the LTC3830 internal oscillator to
lock to the external clock frequency. The LTC3830-1 does
not have this external synchronization function.
The LTC3830 internal oscillator can be externally synchro-
nized from 100kHz to 500kHz. Frequencies above 300kHz
can cause a decrease in the maximum obtainable duty
cycle as rise/fall time and propagation delay take up a
larger percentage of the switch cycle. Circuits using these
frequencies should be checked carefully in applications
where operation near dropout is important—like 3.3V to
2.5V converters. The low period of this clock signal must
not be >100 μ s, or else the LTC3830 enters shutdown
mode.
Figure 5 describes the operation of the external synchro-
nization function. A negative transition at the SHDN pin
forces the internal ramp signal low to restart a new PWM
cycle. Notice that with the traditional sync method, the
ramp amplitude is lowered as the external clock frequency
goes higher. The effect of this decrease in ramp amplitude
increases the open-loop gain of the controller feedback
loop. As a result, the loop crossover frequency increases
and it may cause the feedback loop to be unstable if the
phase margin is insufficient.
To overcome this problem, the LTC3830 monitors the
peak voltage of the ramp signal and adjusts the oscillator
charging current to maintain a constant ramp peak.
V CC
PV CC2
PV CC1
G1
V IN
Q1
SHDN
INTERNAL
CIRCUITRY
L O
V OUT
G2
Q2
+
C OUT
200kHz
FREE RUNNING
RAMP SIGNAL
WITH EXT SYNC
LTC3830 (16-LEAD)
3830 F6
TRADITIONAL
SYNC METHOD
WITH EARLY
RAMP
TERMINATION
RAMP SIGNAL
Figure 6. 16-Lead Power Supplies
RAMP AMPLITUDE
ADJUSTED
V CC /PV CC2
PV CC1
G1
V IN
Q1
LTC3830
KEEPS RAMP
INTERNAL
CIRCUITRY
L O
V OUT
AMPLITUDE
CONSTANT
UNDER SYNC
G2
Q2
+
C OUT
3830 F05
LTC3830 (8-LEAD)
3830 F7
Figure 5. External Synchronization Operation
Figure 7. 8-Lead Power Supplies
3830fa
11
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LTC3830EGN#TRPBF 功能描述:IC REG CTRLR BUCK PWM VM 16-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)
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