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参数资料
| 型号： | ISL6842IBZ |
| 厂商： | Intersil |
| 文件页数： | 9/13页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BST FLYBK ISO 8SOIC |
| 标准包装： | 980 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 2MHz |
| 占空比： | 100% |
| 电源电压： | 15 V ~ 18 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-SOIC（0.154"，3.90mm 宽） |
| 包装： | 管件 |
ISL6840, ISL6841, ISL6842, ISL6843, ISL6844, ISL6845
Pin Descriptions
RTCT - This is the oscillator timing control pin. The
operational frequency and maximum duty cycle are set by
connecting a resistor, RT, between VREF and this pin and a
timing capacitor, CT, from this pin to GND. The oscillator
produces a sawtooth waveform with a programmable
frequency range up to 2.0MHz. The charge time, t C , the
discharge time, t D , the switching frequency, f, and the
maximum duty cycle, Dmax, can be calculated from
Equations 1, 2, 3 and 4:
Functional Description
Features
The ISL684x current mode PWMs make an ideal choice for
low-cost flyback and forward topology applications. With its
greatly improved performance over industry standard parts,
it is the obvious choice for new designs or existing designs
which require updating.
Oscillator
The ISL684x family of controllers have a sawtooth oscillator
t
C
≈ 0.583 ? RT ? CT
(EQ. 1)
with a programmable frequency range to 2MHz, which can
be programmed with a resistor from VREF and a capacitor to
t D ≈ – RT ? CT ? ln ? ---------------------------------------------- ?
D = t ? f
f = 1 ? ( tC + tD )
C
0.0083 ? RT – 4.3
? 0.0083 ? RT – 2.4 ?
(EQ. 2)
(EQ. 3)
(EQ. 4)
GND on the RTCT pin. (Please refer to Figure 4 for the
resistor and capacitance required for a given frequency.)
Soft-Start Operation
Soft-start must be implemented externally. One method,
illustrated in Figure 5, clamps the voltage on COMP.
Figure 4 may be used as a guideline in selecting the
capacitor and resistor values required for a given frequency.
COMP - COMP is the output of the error amplifier and the
input of the PWM comparator. The control loop frequency
compensation network is connected between the COMP and
FB pins.
FB - The output voltage feedback is connected to the
VREF
COMP
GND
inverting input of the error amplifier through this pin. The
non-inverting input of the error amplifier is internally tied to a
reference voltage.
FIGURE 5. SOFT-START
CS - This is the current sense input to the PWM comparator.
The range of the input signal is nominally 0V to 1.0V and has
an internal offset of 100mV.
GND - GND is the power and small signal reference ground
for all functions.
OUT - This is the drive output to the power switching device.
It is a high current output capable of driving the gate of a
power MOSFET with peak currents of 1.0A.
VDD - V DD is the power connection for the device. The total
supply current will depend on the load applied to OUT. Total
I DD current is the sum of the operating current and the
average output current. Knowing the operating frequency, f,
and the MOSFET gate charge, Qg, the average output
current can be calculated in Equation 5:
I OUT = Qg × f (EQ. 5)
To optimize noise immunity, bypass V DD to GND with a
ceramic capacitor as close to the VDD and GND pins as
possible.
VREF - The 5.00V reference voltage output. +1.0/-1.5%
tolerance over line, load and operating temperature. Bypass
to GND with a 0.1μF to 3.3μF capacitor to filter this output as
needed.
9
Gate Drive
The ISL684x family are capable of sourcing and sinking 1A
peak current. To limit the peak current through the IC, an
optional external resistor may be placed between the
totem-pole output of the IC (OUT pin) and the gate of the
MOSFET. This small series resistor also damps any
oscillations caused by the resonant tank of the parasitic
inductances in the traces of the board and the FET’s input
capacitance.
Slope Compensation
For applications where the maximum duty cycle is less than
50%, slope compensation may be used to improve noise
immunity, particularly at lighter loads. The amount of slope
compensation required for noise immunity is determined
empirically, but is generally about 10% of the full scale
current feedback signal. For applications where the duty
cycle is greater than 50%, slope compensation is required to
prevent instability. The minimum amount of slope
compensation required corresponds to 1/2 the inductor
downslope. Adding excessive slope compensation,
however, results in a control loop that behaves more as a
voltage mode controller than as a current mode controller.
Slope compensation may be added to the CS signal shown
in Figure 7.
FN9124.11
February 23, 2012
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相关代理商/技术参数 |
参数描述 |
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| ISL6842IBZ-T | 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) |
| ISL6842IRZ | 制造商:Rochester Electronics LLC 功能描述:- Bulk 制造商:Intersil Corporation 功能描述: |
| ISL6842IRZ-T | 功能描述:IC REG CTRLR BST FLYBK ISO 8-DFN 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) |
| ISL6842IU | 功能描述:IC REG CTRLR BST FLYBK ISO 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:100% 电源电压:8.2 V ~ 30 V 降压:无 升压:无 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:0°C ~ 70°C 封装/外壳:8-DIP（0.300"，7.62mm） 包装:管件 产品目录页面:1316 (CN2011-ZH PDF) |
| ISL6842IU-T | 功能描述:IC REG CTRLR BST FLYBK ISO 8MSOP RoHS:否 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 切换控制器 系列:- 标准包装:2,500 系列:- PWM 型:电流模式 输出数:1 频率 - 最大:500kHz 占空比:100% 电源电压:8.2 V ~ 30 V 降压:无 升压:无 回扫:是 反相:无 倍增器:无 除法器:无 Cuk:无 隔离:是 工作温度:0°C ~ 70°C 封装/外壳:8-DIP（0.300"，7.62mm） 包装:管件 产品目录页面:1316 (CN2011-ZH PDF) |
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