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参数资料
| 型号： | ISL8844AAUZ-T |
| 厂商： | Intersil |
| 文件页数： | 12/15页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK ISO 8MSOP |
| 产品培训模块： | Solutions for Industrial Control Applications |
| 标准包装： | 2,500 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 2MHz |
| 占空比： | 50% |
| 电源电压： | 9 V ~ 30 V |
| 降压： | 是 |
| 升压： | 是 |
| 回扫： | 是 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 是 |
| 工作温度： | -40°C ~ 105°C |
| 封装/外壳： | 8-TSSOP，8-MSOP（0.118"，3.00mm 宽） |
| 包装： | 带卷 (TR) |
ISL8840A, ISL8841A, ISL8842A, ISL8843A, ISL8844A, ISL8845A
The current sense signal at the end of the ON time for CCM
operation is:
V CS = ------------------------ ? I O + -------------------------------------------- ?
N S ? R CS ? ( 1 – D ) ? V O ? f sw ?
N P ? 2L s ?
V
(EQ. 13)
VREF
where V CS is the voltage across the current sense resistor,
R9
L s is the secondary winding inductance, and I O is the output
current at current limit. Equation 13 assumes the voltage
R6
CS
drop across the output rectifier is negligible.
Since the peak current limit threshold is 1.00V, the total
current feedback signal plus the external ramp voltage must
sum to this value when the output load is at the current limit
threshold.
RTCT
C4
FIGURE 6. SLOPE COMPENSATION
V e + V CS = 1
(EQ. 14)
Assuming the designer has selected values for the RC filter
(R 6 and C 4 ) placed on the CS pin, the value of R 9 required
R CS = -----------------------------------------------------------------------------------------------------------------------------------------------------
? --- + 0.5
?
D ? f sw ? V IN ? ( 1 – D ) ? V O ? f sw ?
π
------------------------------- ? ? ------------------ – 1 ? + ------ s - ? ? I O + -------------------------------------------- ?
? 1 – D ?
L p N p ? 2L s ?
2.05D ? R 6
V e = ----------------------------
Substituting Equations 12 and 13 into Equation 14 and
solving for R CS yields
1
1
N
? ?
(EQ. 15)
to add the appropriate external ramp can be found by
superposition.
V (EQ. 16)
R 6 + R 9
The factor of 2.05 in Equation 16 arises from the peak
amplitude of the sawtooth waveform on RTCT minus a
base-emitter junction drop. That voltage multiplied by the
maximum duty cycle is the voltage source for the slope
( 2.05D – V e ) ? R 6
R 9 = ----------------------------------------------
Adding slope compensation is accomplished in the
ISL884xA using an external buffer transistor and the RTCT
signal. A typical application sums the buffered RTCT signal
with the current sense feedback and applies the result to the
compensation. Rearranging to solve for R 9 yields:
Ω
V e
(EQ. 17)
CS pin as shown in Figure 6.
The value of R CS determined in Equation 15 must be
rescaled so that the current sense signal presented at the
CS pin is that predicted by Equation 13. The divider created
by R 6 and R 9 makes this necessary.
R ′ CS = --------------------- ? R CS
12
R 6 + R 9
R 9
(EQ. 18)
FN6320.3
April 18, 2007
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| ISL8844AMBZ | 功能描述:IC REG CTRLR BST FLYBK ISO 8SOIC 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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