参数资料
型号: NCP1595MNT2G
厂商: ON Semiconductor
文件页数: 11/13页
文件大小: 0K
描述: IC REG BUCK SYNC ADJ 1.5A 6DFN
标准包装: 3,000
类型: 降压(降压)
输出类型: 可调式
输出数: 1
输出电压: 可调至 0.8V
输入电压: 4 V ~ 5.5 V
PWM 型: 电流模式
频率 - 开关: 1MHz
电流 - 输出: 1.5A
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: 6-VDFN 裸露焊盘
包装: 带卷 (TR)
供应商设备封装: 6-DFN(3x3)
NCP1595, NCP1595A, NCP1595C
APPLICATION INFORMATION
Programming the Output Voltage
The output voltage is set using a resistive voltage divider
from the output voltage to FB pin (see Figure 25). So the
C OUT(min) +
I ripple
8 @ f @ V ripple
(eq. 3)
V out + V FB @
output voltage is calculated according to Eq.1.
R 1 ) R 2
R 2
V out
R1
FB
R2
Figure 25. Output divider
(eq. 1)
Where V ripple is the allowed output voltage ripple.
The required ESR for this amount of ripple can be
calculated by equation 5.
V ripple
ESR + (eq. 4)
I ripple
Based on Equation 2 to choose capacitor and check its
ESR according to Equation 3. If ESR exceeds the value from
Eq.4, multiple capacitors should be used in parallel.
Ceramic capacitor can be used in most of the applications.
In addition, both surface mount tantalum and through ? hole
aluminum electrolytic capacitors can be used as well.
Maximum Output Capacitor
NCP1595/A/C family has internal 1 ms fixed soft ? start
and overcurrent limit. It limits the maximum allowed output
capacitor to startup successfully. The maximum allowed
output capacitor can be determined by the equation:
C out(max) +
C in(min) + I out(max) @ D max @
f @ V in(ripple)
Inductor Selection
The inductor is the key component in the switching
regulator. The selection of inductor involves trade ? offs
among size, cost and efficiency. The inductor value is
selected according to the equation 2.
V out V out
L + @ 1 * (eq. 2)
f @ I ripple V in(max)
Where V out ? the output voltage;
f ? switching frequency, 1.0 MHz;
I ripple ? Ripple current, usually it’s 20% ? 30% of output
current;
V in(max) ? maximum input voltage.
Choose a standard value close to the calculated value to
maintain a maximum ripple current within 30% of the
maximum load current. If the ripple current exceeds this
30% limit, the next larger value should be selected.
The inductor ’s RMS current rating must be greater than
the maximum load current and its saturation current should
be about 30% higher. For robust operation in fault conditions
(start ? up or short circuit), the saturation current should be
high enough. To keep the efficiency high, the series
resistance (DCR) should be less than 0.1 W , and the core
material should be intended for high frequency applications.
Output Capacitor Selection
The output capacitor acts to smooth the dc output voltage
and also provides energy storage. So the major parameter
necessary to define the output capacitor is the maximum
allowed output voltage ripple of the converter. This ripple is
related to capacitance and the ESR. The minimum
capacitance required for a certain output ripple can be
D i p ? p
I lim(min) * I load(max) * 2
(eq. 5)
V out T SS(min)
Where T SS(min) is the minimum soft ? start period (1ms);
D iPP is the current ripple.
This is assuming that a constant load is connected. For
example, with 3.3 V/2.0 A output and 20% ripple, the max
allowed output capacitors is 546 m F.
Input Capacitor Selection
The input capacitor can be calculated by Equation 6.
1
(eq. 6)
Where V in(ripple) is the required input ripple voltage.
V out
D max + is the maximum duty cycle. (eq. 7)
V in(min)
Power Dissipation
The NCP1595/A/C is available in a thermally enhanced
6 ? pin, DFN. When the die temperature reaches +185 ° C, the
NCP1595/A/C shuts down (see the Thermal ? Overload
Protection section). The power dissipated in the device is the
sum of the power dissipated from supply current (PQ),
power dissipated due to switching the internal power
MOSFET (P SW ), and the power dissipated due to the RMS
current through the internal power MOSFET (PON). The
total power dissipated in the package must be limited so the
junction temperature does not exceed its absolute maximum
rating of +150 ° C at maximum ambient temperature.
calculated by Equation 4.
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