参数资料
| 型号： | ISL6753AAZA |
| 厂商： | Intersil |
| 文件页数： | 11/15页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM/VM 16-QSOP |
| 标准包装： | 98 |
| PWM 型： | 电流/电压模式 |
| 输出数： | 4 |
| 频率 - 最大： | 2MHz |
| 占空比： | 100% |
| 电源电压： | 9 V ~ 16 V |
| 降压： | 无 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 105°C |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 管件 |
| 产品目录页面： | 1243 (CN2011-ZH PDF) |
ISL6753
For simplicity, idealized components have been used for this
discussion, but the effect of magnetizing inductance must be
considered when determining the amount of external ramp
Assuming the designer has selected values for the RC filter
placed on the CS pin, the value of R9 required to add the
appropriate external ramp can be found by superposition.
V e – ? V CS = -------------------------------------------------------------------------------
to add. Magnetizing inductance provides a degree of slope
compensation to the current feedback signal and reduces
the amount of external ramp required. The magnetizing
( D ( V CTBUF – 0.4 ) + 0.4 ) ? R6
R6 + R9
V
(EQ. 22)
? I P = -------------------------------
V IN ? DT SW
( D ( V CTBUF – 0.4 ) – V e + ? V CS + 0.4 ) ? R6
V e – ? V CS
inductance adds primary current in excess of what is
reflected from the inductor current in the secondary.
A
L m
(EQ. 19)
Rearranging to solve for R9 yields
R9 = -------------------------------------------------------------------------------------------------------------------
?
(EQ. 23)
where V IN is the input voltage that corresponds to the duty
cycle D and Lm is the primary magnetizing inductance. The
effect of the magnetizing current at the current sense
resistor, R CS , is
The value of R CS determined in Equation 18 must be
rescaled so that the current sense signal presented at the
CS pin is that predicted by Equation 16. The divider created
by R6 and R9 makes this necessary.
? V CS = --------------------------
R ′ CS = ---------------------- ? R CS
? I P ? R CS
N CT
V
(EQ. 20)
R6 + R9
R9
(EQ. 24)
R CS = --------------------------------------------------------------------------------------------------------------------------------------
N S ? DT SW ? ? ? V IN ? DT SW
-------- ? ? I O + ----------------- ? ? V IN ? ------- S - – V O ? ? + -------------------------------
If ? V CS is greater than or equal to Ve, then no additional
slope compensation is needed and R CS becomes
N CT
N
N P ? 2L O ? N P ? ? L m
(EQ. 21)
If ? V CS is less than Ve, then Equation 18 is still valid for the
value of R CS , but the amount of slope compensation added
by the external ramp must be reduced by ? V CS .
Adding slope compensation is accomplished in the ISL6753
using the CTBUF signal. CTBUF is an amplified
representation of the sawtooth signal that appears on the CT
pin. It is offset from ground by 0.4V and is 2x the peak-to-
peak amplitude of CT (0.4 - 4.4V). A typical application sums
this signal with the current sense feedback and applies the
result to the CS pin as shown in Figure 7.
1
2 CTBUF
3
Example:
V IN = 280V
V O = 12V
L O = 2.0 μ H
Np/Ns = 20
Lm = 2mH
I O = 55A
Oscillator Frequency, Fsw = 400kHz
Duty Cycle, D = 85.7%
N CT = 50
R6 = 499 ?
Solve for the current sense resistor, R CS , using Equation 18.
R CS = 15.1 ? .
Determine the amount of voltage, Ve, that must be added to
the current feedback signal using Equation 15.
Ve = 153mV
R CS
R6
R9
C4
4
5
6
7
8 CS
ISL6753
Next, determine the effect of the magnetizing current from
Equation 20.
? V CS = 91mV
Using Equation 23, solve for the summing resistor, R9, from
CTBUF to CS.
R9 = 30.1k ?
Determine the new value of R CS , R’ CS , using Equation 24.
R’ CS = 15.4 ?
The above discussion determines the minimum external
FIGURE 7. ADDING SLOPE COMPENSATION
11
ramp that is required. Additional slope compensation may be
considered for design margin.
FN9182.2
April 4, 2006
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| ISL6753AAZA-T | 功能描述:IC REG CTRLR PWM CM/VM 16-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
| ISL6754AAZA | 功能描述:IC REG CTRLR PWM CM/VM 20-QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:275kHz 占空比:50% 电源电压:18 V ~ 110 V 降压:无 升压:无 回扫:无 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:-40°C ~ 85°C 封装/外壳:8-SOIC（0.154"，3.90mm 宽） 包装:带卷 (TR) |
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