参数资料
型号: LTC3447EDD#TRPBF
厂商: Linear Technology
文件页数: 8/16页
文件大小: 0K
描述: IC REG BUCK SYNC ADJ 0.6A 10DFN
标准包装: 2,500
类型: 降压(降压)
输出类型: 可调式
输出数: 1
输出电压: 0.69 V ~ 2.05 V
输入电压: 2.5 V ~ 5.5 V
PWM 型: 电流模式,混合
频率 - 开关: 1MHz
电流 - 输出: 600mA
同步整流器:
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 10-WFDFN 裸露焊盘
包装: 带卷 (TR)
供应商设备封装: 10-DFN(3x3)
LTC3447
OPERATIO
the user should calculate the power dissipation when
the LTC3447 is used at 100% duty cycle with low input
voltage (See Thermal Considerations in the Applications
Information section).
Low Supply Operation
The LTC3447 will operate with input supply voltages as
low as 2.5V, but the maximum allowable output current
is reduced at this low voltage. Figure 4 shows the reduc-
tion in the maximum output current as a function of input
voltage for various output voltages.
for duty cycles >40%; however, the LTC3447 uses a
patent-pending scheme that counteracts this compensat-
ing ramp, which allows the maximum inductor peak current
to remain unaffected throughout all duty cycles.
DAC
The I 2 C interface is used to control the internal voltage
DAC for the buck regulator. The output voltage range is
0.69V to 2.05V in 21.6mV steps. The default DAC setting
is 100000 which equates to a 1.38V output voltage. Output
voltage transitions begin once the I 2 C interface receives
the STOP command.
Slope Compensation and Inductor Peak Current
Slope compensation provides stability in constant fre-
quency architectures by preventing subharmonic oscil-
lations at high duty cycles. It is accomplished internally
by adding a compensating ramp to the inductor current
signal at duty cycles in excess of 40%. Normally, this
results in a reduction of maximum inductor peak current
Slew Rate
The LTC3447 has a slew rate of approximately 11mV/μs.
The slew rate is controlled by the RC time constant of a
low pass ?lter at the voltage DAC output. Figure 5 shows
a typical transition from min to max DAC settings.
1200
T A = 25 ° C
BURST MODE OPERATION
1100
1000
900
800
700
DAC = MIN
DAC = MAX
500mV/DIV
200mA/DIV
5V/DIV
V IN = 3.6V
V OUT
INDUCTOR CURRENT
PGOOD
2.5
3.0
3.5 4.0 4.5
SUPPLY VOLTAGE (V)
5.0
5.5
100 μ s/DIV
3447 F04
SDA
Figure 4 . Maximum Load Current vs Supply Voltage
Figure 5 .Transition from DAC = MIN to DAC = MAX
SCL
1-7
8
9
1-7
8
9
1-7
8
9
S
P
START
ADDRESS
R/W
ACK
DATA
ACK
DATA
ACK
ST0P
COMMAND
COMMAND
3447 TD02
Figure 6. Typical I 2 C Write Protocol
3447f
8
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