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| 型号： | ISL6840IBZ |
| 厂商： | INTERSIL CORP |
| 元件分类： | 稳压器 |
| 英文描述： | Improved Industry Standard Single-Ended Current Mode PWM Controller |
| 中文描述： | 1 A SWITCHING CONTROLLER, 2000 kHz SWITCHING FREQ-MAX, PDSO8 |
| 封装： | ROHS COMPLIANT, PLASTIC, MS-012AA, SOIC-8 |
| 文件页数： | 8/11页 |
| 文件大小： | 307K |
| 代理商： | ISL6840IBZ |
8
FN9124.6
June 28, 2005
V
DD
-
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 from:
To optimize noise immunity, bypass V
DD
to GND with a
ceramic capacitor as close to the V
DD
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 0.1
μ
F to 3.3
μ
F capacitor to filter this output as
needed.
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 controllers have a sawtooth oscillator with a
programmable frequency range to 2MHz, which can be
programmed with a resistor from VREF and a capacitor to
GND on the RTCT pin. (Please refer to
Fig. 4
for the resistor
and capacitance required for a given frequency.)
Soft-Start Operation
Soft-start must be implemented externally. One method,
illustrated below, clamps the voltage on COMP.
Gate Drive
The ISL684x 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 current mode controller.
Slope compensation may added to the CS signal in the
following manner.
Fault Conditions
A Fault condition occurs if VREF falls below 4.65V. When a
Fault is detected OUT is disabled. When VREF exceeds
4.80V, the Fault condition clears, and OUT is enabled.
Ground Plane Requirements
Careful layout is essential for satisfactory operation of the
device. A good ground plane must be employed. A unique
section of the ground plane must be designated for high di/dt
currents associated with the output stage. V
DD
should be
bypassed directly to GND with good high frequency
capacitors.
I
OUT
Qg
f
×
=
(EQ. 5)
FIGURE 5. SOFT-START
VREF
COMP
GND
I
FIGURE 6. CURRENT SENSE DOWNSLOPE
TIME
C
DOWNSLOPE
CURRENT SENSE SIGNAL
FIGURE 7. SLOPE COMPENSATION
VREF
RTCT
CS
I
ISL6840, ISL6841, ISL6842, ISL6843, ISL6844, ISL6845
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| ISL6840IBZ-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) |
| ISL6840IRZ-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) |
| ISL6840IU | 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) |
| ISL6840IU-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) |
| ISL6840IUZ | 功能描述:电流型 PWM 控制器 CUR MODE PWM 100% DU TY CYCLE 7.0V UVLO RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
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