参数资料
| 型号： | ISL6721AV |
| 厂商： | Intersil |
| 文件页数： | 9/22页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR PWM CM 16-TSSOP |
| 标准包装： | 96 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 1MHz |
| 占空比： | 100% |
| 电源电压： | 9 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： | 16-TSSOP（0.173"，4.40mm 宽） |
| 包装： | 管件 |
ISL6721
Pin Descriptions
SLOPE - Means by which the ISENSE ramp slope may be
increased for improved noise immunity or improved control
loop stability for duty cycles greater than 50%. An internal
current source charges an external capacitor to GND during
each switching cycle. The resulting ramp is scaled and
added to the ISENSE signal.
SYNC - A bidirectional synchronization signal used to
coordinate the switching frequency of multiple units.
Synchronization may be achieved by connecting the SYNC
signal of each unit together or by using an external master
clock signal. The oscillator timing capacitor, C T , is still
required, even if an external clock is used. The first unit to
assert this signal assumes control.
RTCT - This is the oscillator timing control pin. The
operational frequency and maximum duty cycle are set by
connecting a resistor, R T , between V REF and this pin and a
timing capacitor, C T , from this pin to LGND. The oscillator
produces a sawtooth waveform with a programmable
frequency range of 100kHz to 1.0MHz. The charge time, t C ,
the discharge time, t D , the switching frequency, fsw, and the
maximum duty cycle, Dmax, can be calculated from
Equations 1, 2, 3 and 4:
UV - Undervoltage monitor input pin. This signal is
compared to an internal 1.45V reference to detect an
undervoltage condition.
ISENSE - This is the input to the current sense comparators.
The IC has two current sensing comparators, a PWM
comparator for peak current mode control, and an
overcurrent protection comparator. The overcurrent
comparator threshold is adjustable through the ISET pin.
Exceeding the overcurrent threshold will start a delayed
shutdown sequence. Once an overcurrent condition is
detected, the soft-start charge current source is disabled and
a discharge current source is enabled. The soft-start capacitor
begins discharging, and if it discharges to less than 4.375V
(sustained overcurrent threshold), a shutdown condition
occurs and the GATE output is forced low. At this point a
reduced discharge current takes over until the soft-start
voltage reaches 0.27V (reset threshold). The GATE output
remains low until the reset threshold is attained. At this point,
a soft-start cycle begins.
If the overcurrent condition ceases, and then an additional
50μs period elapses before the shutdown threshold is
reached, no shutdown occurs and the soft-start voltage is
allowed to recharge.
t C ≈ 0.655 ? R T ? C T
S
(EQ. 1)
LGND - LGND is a small signal reference ground for all
analog functions on this device.
t D ≈ – R ? C ? LN ? ------------------------------------------- ?
? 0.001 ? R T – 1.9 ?
T T
0.001 ? R T – 3.6
S
(EQ. 2)
PGND - This pin provides a dedicated ground for the output
gate driver. The LGND and PGND pins should be connected
externally using a short printed circuit board trace close to
the IC. This is imperative to prevent large, high frequency
f sw = -----------------
1
t D + t C
Hz
(EQ. 3)
switching currents flowing through the ground metallization
inside the IC. (Decouple V C to PGND with a low ESR 0.1μF
or larger capacitor.)
Dmax = t C ? f sw
(EQ. 4)
GATE - This is the device output. It is a high current power
driver capable of driving the gate of a power MOSFET with
peak currents of 1.0A. This GATE output is actively held low
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
when V CC is below the UVLO threshold.
The output high voltage is clamped to ~13.5V. Voltages
exceeding this clamp value should not be applied to the
GATE pin. The output stage provides very low impedance to
overshoot and undershoot.
FB pins.
VC - This pin is for separate collector supply to the output
The ISL6721 features a built-in full cycle soft-start. Soft-start
is implemented as a clamp on the maximum COMP voltage.
FB - Feedback voltage input connected to the inverting input
of the error amplifier. The non-inverting input of the error
amplifier is internally tied to a reference voltage. Current
sense leading edge blanking is disabled when the FB input
is less than 2.0V.
OV - Overvoltage monitor input pin. This signal is compared
to an internal 2.5V reference to detect an overvoltage
condition.
9
gate drive. Separate V C and PGND helps decouple the IC’s
analog circuitry from the high power gate drive noise.
(Decouple V C to PGND with a low ESR 0.1μF or larger
capacitor.)
VCC - V CC is the power connection for the device. Although
quiescent current, I CC , is low, it is dependent on the
frequency of operation. To optimize noise immunity, bypass
V CC to LGND with a ceramic capacitor as close to the V CC
and LGND pins as possible.
FN9110.6
March 5, 2008
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| ISL6721AV-T | 功能描述:电流型 PWM 控制器 FLEXIBLE SINGLE END CUR MODE PWM 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 |
| ISL6721AVZ | 功能描述:电流型 PWM 控制器 FLEX SNG ENDED CUR MODE PWM CONTRLR 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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