参数资料
| 型号： | ISL8121IRZ |
| 厂商： | Intersil |
| 文件页数： | 10/26页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM VM 24-QFN |
| 标准包装： | 75 |
| PWM 型： | 电压模式 |
| 输出数： | 1 |
| 频率 - 最大： | 2MHz |
| 占空比： | 66% |
| 电源电压： | 4.9 V ~ 5.5 V |
| 降压： | 是 |
| 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 ~ 85°C |
| 封装/外壳： | 24-VFQFN 裸露焊盘 |
| 包装： | 管件 |
ISL8121
has a combined ripple frequency twice the frequency of
one of its phases. In addition, the peak-to-peak
amplitude of the combined inductor currents is
C IN CURRENT
proportionately reduced. Increased ripple frequency and
lower ripple amplitude generally translate to lower per-
channel inductance and/or lower total output capacitance
for any given set of performance specification.
Q1 D-S CURRENT
I L1 + I L2
Q3 D-S CURRENT
I L2
PWM2
( V IN – V OUT ) ? V OUT (EQ. 3)
L ? f S ? V
L ? f S ? V
I L1
PWM1
FIGURE 3. PWM AND INDUCTOR-CURRENT
WAVEFORMS FOR 2-PHASE CONVERTER
Figure 3 illustrates the additive effect on output ripple
frequency. The two channel currents (I L1 and I L2 ),
combine to form the AC ripple current and the DC load
current. The ripple component has two times the ripple
frequency of each individual channel current.
To understand the reduction of ripple current amplitude
in the multi-phase circuit, examine Equation 3, which
represents an individual channel’s peak-to-peak inductor
current.
I L , PP = ----------------------------------------------------------
IN
V IN and V OUT are the input and output voltages,
respectively, L is the single-channel inductor value, and
f S is the switching frequency.
The output capacitors conduct the ripple component of
the inductor current. In the case of multi-phase
converters, the capacitor current is the sum of the ripple
currents from each of the individual channels.
( V IN – N ? V OUT ) ? V OUT (EQ. 4)
I PP = --------------------------------------------------------------------
IN
Peak-to-peak ripple current decreases by an amount
proportional to the number of channels. Output-voltage
ripple is a function of capacitance, capacitor equivalent
series resistance (ESR), and inductor ripple current.
Reducing the inductor ripple current allows the designer
to use fewer or less costly output capacitors (should
output high-frequency ripple be an important design
parameter).
10
FIGURE 4. INPUT CAPACITOR CURRENT AND
INDIVIDUAL CHANNEL CURRENTS IN A
2-PHASE CONVERTER
Another benefit of interleaving is the reduction of input
ripple current. Input capacitance is determined in a large
part by the maximum input ripple current. Multi-phase
topologies can improve overall system cost and size by
lowering input ripple current and allowing the designer to
reduce the cost of input capacitance. The example in
Figure 4 illustrates input currents from a two-phase
converter combining to reduce the total input ripple
current.
RMS current based on load current and duty cycle. The
figure is provided as an aid in determining the optimal
input capacitor solution.
PWM OPERATION
One switching cycle for the ISL8121 is defined as the
time between consecutive PWM pulse terminations (turn-
off of the upper MOSFET on a channel). Each cycle begins
when a switching clock signal commands the upper
MOSFET to go off. The other channel’s upper MOSFET
conduction is terminated 1/2 of a cycle later.
Once a channel’s upper MOSFET is turned off, the lower
MOSFET remains on for a minimum of 1/3 cycle. This
forced off time is required to assure an accurate current
sample. Following the 1/3-cycle forced off time, the
controller enables the upper MOSFET output. Once
enabled, the upper MOSFET output transitions high when
the sawtooth signal crosses the adjusted error-amplifier
output signal, as illustrated in Figure 2. Just prior to the
upper drive turning the MOSFET on, the lower MOSFET
drive turns the freewheeling element off. The upper
MOSFET is kept on until the clock signals the beginning of
the next switching cycle and the PWM pulse is
terminated.
FN6352.2
October 27, 2009
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相关代理商/技术参数 |
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| ISL8121IRZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 24-QFN 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) |
| ISL8121IRZ-TR5453 | 制造商:Intersil Corporation 功能描述:STD. ISL8121IRZ-T WITH GOLD BOND WIRE ONLY - Tape and Reel |
| ISL8126 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Dual/n-Phase Buck PWM Controller with Integrated Drivers |
| ISL8126CRZ | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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) |
| ISL8126CRZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 32-QFN 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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