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参数资料
| 型号： | NCP1599GEVB |
| 厂商： | ON Semiconductor |
| 文件页数： | 12/15页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION NCP1599 |
| 设计资源： | NCP1599GEVB BOM NCP1599GEVB Schematic NCP1599GEVB Gerber Files |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 最低可调至 0.8V |
| 电流 - 输出： | 3A |
| 输入电压： | 3 ~ 5.5 V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 1MHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | NCP1599 |
| 其它名称： | NCP1599GEVBOS |
NCP1599
related to capacitance and the ESR. The minimum
capacitance required for a certain output ripple can be
calculated by Equation 4.
network is to stabilize the control loop and achieve high
performance in terms of the transient response, audio
susceptibility and output impedance. Specifically, the
C OUT(min) +
I ripple
8 @ f @ V ripple
(eq. 3)
compensator is added to increase low frequency magnitude,
extend the 0 dB frequency (crossover frequency), and
improve the phase characteristic.
Where V ripple is the allowed output voltage ripple.
The required ESR for this amount of ripple can be
calculated by equation 5.
Current Mode
Power Stage
LX
V ripple
ESR + (eq. 4)
I ripple
Based on Equation 2 to choose capacitor and check its
Gm
+
?
FB
R1
R2
C FF
ESR
C out
RL
ESR according to Equation 3. If ESR exceeds the value from
Eq.4, multiple capacitors should be used in parallel.
Ceramic capacitors 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.
RGM
0.8 V
+
?
COMP
R C
CC2
C out(max) +
A DC + R G CS A EA (eq. 8)
C in(min) + I out(max) @ D max @
f @ V in(ripple)
V out
f p1 +
2 p @ C out @ R
f ESRZ +
2 p @ C out @ R ESR
Maximum Output Capacitor
NCP1599 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 capacitance can be determined by the equation:
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
maximum allowed output capacitance 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.
D max + is the maximum duty cycle. (eq. 7)
V in(min)
Compensation Design
The NCP1599 is a current mode controller, therefore there
are two feedback loops. The inner feedback loop derives its
feedback from the sensed inductor current, while the outer
loop monitors the output voltage.
The compensation network is designed around the power
components, or the power stage. An isolated schematic of
the error amplifier and the various compensation
components is shown in Figure 26. The error amplifier in
conjunction with the compensation network makes up the
compensator network. The purpose of the compensator
CC1
Figure 26. NCP1599 Compensation Components
There are several different types of compensation that can
be used to improve the frequency response of the control
loop. To determine which compensation scheme to use,
some information about the power stage is needed. Use V in
= V in(min) and R = R min (I out(max) ) when calculating
compensation components.
The DC gain of the voltage feedback loop is given by:
V FB
V out
Where AEA is the error amplifier voltage gain, 560 V/V
(55 db), G CS is the current sense transconductance, 5.0 A/V,
and R is the load resistor value.
The power stage has one pole due to the output capacitor
C out and the load resistor R. It’s located at:
1
(eq. 9)
The power stage may have a zero of importance, if the
output capacitor has a large capacitance and/or a high ESR
value. The zero, due to the ESR and capacitance of the
output capacitor, is located at:
1
(eq. 10)
A compensator is designed to achieve improved
performance and stability. The NCP1599 will typically
require only a single resistor and capacitor for
compensation, but depending on the power stage it could
require three or four external components.
First, a target crossover frequency (fc) for the loop gain
must be selected. The crossover frequency is the bandwidth
http://onsemi.com
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