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| 型号： | ISL6742AAZA |
| 厂商： | Intersil |
| 文件页数： | 10/18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) |
ISL6742
The maximum duty cycle, D, and percent deadtime, DT, can
be calculated from:
The current sense signal applied to the CS pin connects to the
peak current comparator and a sample and hold averaging
t C
D = ----------
t SW
DT = 1 – D
(EQ. 4)
(EQ. 5)
circuit. After a 70ns leading edge blanking (LEB) delay, the
current sense signal is actively sampled during the on-time,
the average current for the cycle is determined, and the result
is amplified by 4x and output on the IOUT pin. If an RC filter is
placed on the CS input, its time constant should not exceed
~50ns or significant error may be introduced on IOUT.
Soft-Start Operation
The ISL6742 features a soft-start using an external capacitor in
conjunction with an internal current source. Soft-start reduces
component stresses and surge currents during start-up.
Upon start-up, the soft-start circuitry limits the error voltage
input (VERR) to a value equal to the soft-start voltage. The
output pulse width increases as the soft-start capacitor voltage
increases. This has the effect of increasing the duty cycle from
zero to the regulation pulse width during the soft-start period.
When the soft-start voltage exceeds the error voltage, soft-
start is completed. Soft-start occurs during start-up and after
recovery from a fault condition. The soft-start charging period
may be calculated using Equation 6:
t = 64.3 ? C
ms
(EQ. 6)
CHANNEL 1 (YELLOW): OUTA
CHANNEL 2 (RED): OUTB
where t is the charging period in ms and C is the value of the
CHANNEL 3 (BLUE): CS
CHANNEL 4 (GREEN): IOUT
soft-start capacitor in μF. The soft-start duration experienced
by the power supply will be less than or equal to this value,
depending on when the feedback loop takes control.
The soft-start voltage is clamped to 4.50V with an overall
tolerance of 2%. It is suitable for use as a “soft-started”
reference provided the current draw is kept well below the
70μA charging current.
The outputs may be inhibited by using the SS pin as a
disable input. Pulling SS below 0.25V forces all outputs low.
An open collector/drain configuration may be used to couple
the disable signal to the SS pin.
Gate Drive
The ISL6742 outputs are capable of sourcing and sinking
10mA (at rated VOH, VOL) and are intended to be used in
conjunction with integrated FET drivers or discrete bipolar
totem pole drivers. The typical ON-resistance of the outputs
is 50 Ω .
Overcurrent Operation
Two overcurrent protection mechanisms are available to the
power supply designer. The first method is cycle-by-cycle
peak overcurrent protection, which provides fast response.
FIGURE 5. CS INPUT vs IOUT
Figure 5 shows the relationship between the CS signal and
IOUT under steady state conditions. IOUT is 4x the average
of CS. Figure 6 shows the dynamic behavior of the current
averaging circuitry when CS is modulated by an external
sine wave. Notice IOUT is updated by the sample and hold
circuitry at the termination of the active output pulse.
The second method is a slower, averaging method, which
produces constant or “brick-wall” current limit behavior. If
CHANNEL 1 (YELLOW): OUTA
CHANNEL 3 (BLUE): CS
CHANNEL 2 (RED): OUTB
CHANNEL 4 (GREEN): IOUT
voltage-mode control is used, the average overcurrent
protection also maintains flux balance in the transformer by
maintaining duty cycle symmetry between half-cycles.
10
FIGURE 6. DYNAMIC BEHAVIOR OF CS vs IOUT
FN9183.2
October 31, 2008
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| ISL6742AAZA-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) |
| ISL6744AABZ | 功能描述:IC REG CTRLR PWM VM 8-SOIC 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) |
| ISL6744AABZ-T | 功能描述:IC REG CTRLR PWM VM 8-SOIC 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) |
| ISL6744AAUZ | 功能描述:IC REG CTRLR PWM VM 8-MSOP 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) |
| ISL6744AAUZ-T | 功能描述:IC REG CTRLR PWM VM 8-MSOP 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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