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参数资料
| 型号： | LMZ10504EXTTZX |
| 厂商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分类： | 稳压器 |
| 英文描述： | 6.7 A SWITCHING REGULATOR, 1160 kHz SWITCHING FREQ-MAX, PSSO7 |
| 封装： | 10.16 X 13.77 MM, 4.57 MM HEIGHT, ROHS COMPLIANT, TO-PMOD, 7 PIN |
| 文件页数： | 5/22页 |
| 文件大小： | 1383K |
| 代理商： | LMZ10504EXTTZX |
Tracking - Equal Soft-Start Time
One way to use the tracking feature is to design the tracking
resistor divider so that the master supply output voltage,
V
OUT1, and the LMZ10504EXT output voltage, VOUT2, both
rise together and reach their target values at the same time.
This is termed ratiometric startup. For this case, the equation
governing the values of tracking divider resistors R
trkb and
R
trkt is given by
The above equation includes an offset voltage, of 200 mV, to
ensure that the final value of the SS pin voltage exceeds the
reference voltage of the LMZ10504EXT. This offset will cause
the LMZ10504EXT output voltage to reach regulation slightly
before the master supply. A value of 33 k
1% is recom-
mended for R
trkt as a compromise between high precision and
low quiescent current through the divider while minimizing the
effect of the 2 A soft-start current source.
For example, if the master supply voltage V
OUT1 is 3.3V and
the LMZ10504EXT output voltage was 1.8V, then the value
of R
trkb needed to give the two supplies identical soft-start
times would be 14.3 k
. A timing diagram for this example,
the equal soft-start time case, is shown below.
30118459
Tracking - Equal Slew Rates
Alternatively, the tracking feature can be used to have similar
output voltage ramp rates. This is referred to as simultaneous
startup. In this case, the tracking resistors can be determined
based on the following equation
and to ensure proper overdrive of the SS pin
V
OUT2 < 0.8 x V OUT1
For the example case of V
OUT1 = 5V and VOUT2 = 2.5V, with
R
trkt set to 33 k as before, Rtrkb is calculated from the above
equation to be 15.5 k
. A timing diagram for the case of equal
slew rates is shown below.
30118461
Pre-Bias Startup Capability
At startup, the LMZ10504EXT is in a pre-biased state when
the output voltage is greater than zero. This often occurs in
many multi-rail applications such as when powering an ASIC,
FPGA, or DSP. The output can be pre-biased in these appli-
cations through parasitic conduction paths from one supply
rail to another. Even though the LMZ10504EXT is a syn-
chronous converter, it will not pull the output low when a pre-
bias condition exists. The LMZ10504EXT will not sink current
during startup until the soft-start voltage exceeds the voltage
on the FB pin. Since the device does not sink current it pro-
tects the load from damage that might otherwise occur if
current is conducted through the parasitic paths of the load.
Current Limit
When a current greater than the output current limit (I
OCL) is
sensed, the on-time is immediately terminated and the low
side MOSFET is activated. The low side MOSFET stays on
for the entire next four switching cycles. During these skipped
pulses, the voltage on the soft-start pin is reduced by dis-
charging the soft-start capacitor by a current sink on the soft-
start pin of nominally 14 A. Subsequent over-current events
will drain more and more charge from the soft-start capacitor,
effectively decreasing the reference voltage as the output
droops due to the pulse skipping. Reactivation of the soft-start
circuitry ensures that when the over-current situation is re-
moved, the part will resume normal operation smoothly.
Over-Temperature Protection
When the LMZ10504EXT senses a junction temperature
greater than 145°C (typ.), both switching MOSFETs are
turned off and the part enters a standby state. Upon sensing
a junction temperature below 135°C (typ.), the part will re-
initiate the soft-start sequence and begin switching once
again.
13
www.national.com
LMZ10504EXT
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LMZ10504EXTTZX/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LMZ10504TZ-ADJ | 制造商:NSC 制造商全称:National Semiconductor 功能描述:4A SIMPLE SWITCHER?Power Module with 5.5V Maximum Input Voltage |
| LMZ10504TZ-ADJ/NOPB | 功能描述:直流/直流开关转换器 5V,4A PWR MODULE RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| LMZ10504TZE-ADJ | 制造商:NSC 制造商全称:National Semiconductor 功能描述:4A SIMPLE SWITCHER?Power Module with 5.5V Maximum Input Voltage |
| LMZ10504TZE-ADJ/NOPB | 功能描述:直流/直流开关转换器 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
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