参数资料
型号: LTC3444EDD#TRPBF
厂商: Linear Technology
文件页数: 9/20页
文件大小: 0K
描述: IC DC/DC CONV WCDMA 8-DFN
标准包装: 2,500
应用: 转换器,WCDMA 功率放大器应用
输入电压: 2.75 V ~ 5.5 V
输出数: 1
输出电压: 0.5 V ~ 5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 8-WFDFN 裸露焊盘
供应商设备封装: 8-DFN-EP(3x3)
包装: 带卷 (TR)
LTC3444
OPERATIO
Reverse Current Limit
The LTC3444 always operates in forced continuous con-
duction mode. The reverse current limit amplifier moni-
tors the inductor current from the output through switch
D. Once the negative inductor current exceeds 3A mini-
mum, the LTC3444 will shut off switch D. The high reverse
current is required to meet the transient slew require-
ments for WCDMA power amplifiers.
Output Overvoltage Protection
The LTC3444 provides output overvoltage protection. If
the output voltage exceeds 5.3V typical, P-channel MOSFET
switches A and D are turned off and N-channel MOSFET
switches B and C are turned on. Normal switching will
resume once the output voltage drops below ~5.1V. If the
condition which caused the output overvoltage is still
present the output will charge up to 5.3V again and the
overvoltage cycle will be repeat. Normal output regulation
will resume once the condition responsible for the output
overvoltage is removed.
Soft-Start
The soft-start function is initiated when the SHDN pin is
brought above 1.4V and the LTC3444 is out of UVLO
(above minimum input operating specs). The LTC3444 is
enabled but the PWM duty cycle is clamped via the error
amp output. The soft-start time is internally set to 250 μ s
to minimize output overshoot. A detailed diagram of this
function is shown in Figure 2.
V IN
SOFT-START
CLAMP
ERROR AMP
20 μ A
+
1.22V
TO PWM V CI
COMPARATORS
C SS
I SS
FB
V C
SHDN
1V
8
7
1
3444 F02
Figure 2. Soft-Start Circuitry
3444fb
9
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