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| 型号： | ISL6740EVAL2 |
| 厂商： | Intersil |
| 文件页数： | 11/28页 |
| 文件大小： | 0K |
| 描述： | EVALUATION BOARD 2 ISL6740 |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 功率 - 输出： | 96W |
| 输出电压： | 12V |
| 电流 - 输出： | 8A |
| 输入电压： | 36 ~ 75 V |
| 稳压器拓扑结构： | 降压 |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | ISL6740 |
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ISL6740, ISL6741
t C ≈ 0.5 ? R TC ? C T
S
The ISL6740, ISL6741 features a built-in soft-start. Soft-start is
implemented as a clamp on the error voltage input.
OTS - The non-inverting input to the over-temperature shutdown
comparator. The signal input at this pin is compared to an
internal threshold of V REF /2. If the voltage at this pin exceeds the
threshold, the Fault signal is asserted and the outputs are
disabled until the condition clears. There is a nominal 25 μ A
switched current source used for hysteresis. The amount of
hysteresis is adjustable by varying the source impedance of the
signal into this pin.
OTS may be used to monitor parameters other than temperature,
such as voltage. Any signal for which a high out-of-bounds
monitor is desired may utilize the OTS comparator.
FAULT - The Fault signal is asserted high whenever the outputs,
OUTA and OUTB, are disabled. This occurs during an over-
temperature fault, an input UV fault, a V REF UV fault, or during an
overcurrent (ISL6740) or short circuit shutdown fault. Fault can
be used to disable synchronous rectifiers whenever the outputs
are disabled.
Fault is a three-state output and is high impedance during the
soft-start cycle. Adding a pull-up resistor to VREF or a pull-down
resistor to ground determines the state of Fault during soft-start.
This feature allows the designer to use the Fault signal to enable
or disable output synchronous rectifiers during soft-start.
UV - Undervoltage monitor input pin. A resistor divider between
the input source voltage and GND sets the undervoltage lock out
threshold. The signal is compared to an internal 1.00V reference
to detect an undervoltage or inhibit condition.
CS - This is the input to the current sense comparator(s). The IC
has the PWM comparator for peak current mode control
(ISL6741) and an overcurrent protection comparator. The
overcurrent comparator threshold is set at 0.600V nominal.
The CS pin is shorted to GND at the end of each switching cycle.
Depending on the current sensing source impedance, a series
input resistor may be required due to the delay between the
internal clock and the external power switch. This delay may
allow an overlap such that the CS signal may be discharged while
the current signal is still active. If the current sense source is low
impedance, it will cause increased power dissipation.
ISL6740 - Exceeding the overcurrent threshold will start a
delayed shutdown sequence. Once an overcurrent condition is
detected, the soft-start charge current source is disabled. The
soft-start capacitor begins discharging through a 25 μ A current
source, and if it discharges to less than 4.25V (Sustained
Overcurrent Threshold), a shutdown condition occurs and the
OUTA and OUTB outputs are forced low. When the soft-start
voltage reaches 0.27V (Reset Threshold) a soft-start cycle begins.
An overcurrent condition must be absent for 50 μ s before the
delayed shutdown control resets. If the overcurrent condition
ceases, and an additional 50 μ s period elapses before the
shutdown threshold is reached, no shutdown occurs. The SS
current limit characteristic of peak current mode control limits
the output current to acceptable levels.
GND - Reference and power ground for all functions on this
device. Due to high peak currents and high frequency operation,
a low impedance layout is necessary. Ground planes and short
traces are highly recommended.
OUTA and OUTB - Alternate half cycle output stages. Each output
is capable of 0.5A peak currents for driving logic level power
MOSFETs or MOSFET drivers. Each output provides very low
impedance to overshoot and undershoot.
VREF - The 5.00V reference voltage output. +1%/-2% tolerance
over line, load and operating temperature. Bypass to GND with a
0.047 μ F to 2.2 μ F ceramic capacitor. Capacitors outside of this
range may cause oscillation.
SS - Connect the soft-start timing capacitor between this pin and
GND to control the duration of soft-start. The value of the
capacitor determines the rate of increase of the duty cycle during
start up, controls the overcurrent shutdown delay (ISL6740), and
the overcurrent and short circuit hiccup restart period.
SCSET - Sets the duty cycle threshold that corresponds to a short
circuit condition. A resistive divider between R TC and GND or R TD
and GND, or a voltage between 0V and 2V may be used to adjust
the SCSET threshold. If using a resistor divider from either RTC or
RTD, the impedance to GND affects the oscillator timing and
should be considered when determining the oscillator timing
components. Connecting SCSET to GND disables short circuit
shutdown and hiccup.
Functional Description
Features
The ISL6740, ISL6741 PWMs are an excellent choice for low cost
bridge and push-pull topologies for applications requiring
accurate duty cycle and deadtime control. With its many
protection and control features, a highly flexible design with
minimal external components is possible. Among its many
features are current mode control (ISL6741), adjustable soft-
start, overcurrent protection, thermal protection, bidirectional
synchronization, fault indication, and adjustable frequency.
Oscillator
The ISL6740, ISL6741 have an oscillator with a programmable
frequency range to 2MHz, which can be programmed with two
resistors and capacitor. The use of three timing elements, R TC ,
R TD , and C T allow great flexibility and precision when setting the
oscillator frequency.
The switching period may be considered the sum of the timing
capacitor charge and discharge durations. The charge duration is
determined by R TC and C T . The discharge duration is determined
by R TD and C T .
(EQ. 2)
t SW = t C + t D = -----------
charging current is re-enabled and the soft-start voltage is
allowed to recover.
ISL6741 - The ISL6741 current mode controller does not
shutdown due to an overcurrent condition. The pulse-by-pulse
11
t D ≈ 0.02 ? R TD ? C T
1
F SW
S
S
(EQ. 3)
(EQ. 4)
FN9111.6
December 2, 2011
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL6740EVAL2Z | 功能描述:EVALUATION BOARD 2 ISL6740 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:- 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL6740EVAL3Z | 制造商:Intersil Corporation 功能描述:ISL6740 EVALUATION BOARD 3 - ROHS COMPLIANT - SOIC - DSL - Bulk 制造商:Intersil Corporation 功能描述:Power Management IC Development Tools ISL6740 EVAL RD 3 ROHS CMPL DSL |
| ISL6740IB | 功能描述:IC REG CTRLR PWM VM 16-SOIC 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) |
| ISL6740IB-T | 功能描述:IC REG CTRLR PWM VM 16-SOIC 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) |
| ISL6740IBZ | 功能描述:电压模式 PWM 控制器 VOLT PWM MODE CONTRL 16LD NSOIC RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
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