参数资料
| 型号： | ISL8121IRZ |
| 厂商： | Intersil |
| 文件页数： | 24/26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
Consult with the manufacturer of the load on specific
decoupling requirements.
Use only specialized low-ESR capacitors intended for
Figure 27; it provides the total ripple current as a
function of duty cycle and number of active channels,
normalized to the parameter K NORM at zero duty cycle.
L ? F SW
switching-regulator applications for the bulk capacitors.
The bulk capacitor’s ESR determines the output ripple
voltage and the initial voltage drop following a high slew-
V OUT
K NORM = --------------------
(EQ. 32)
Δ I TOTAL = K NORM ? K CM
rate transient’s edge. In most cases, multiple capacitors
of small case size perform better than a single large case
capacitor.
Bulk capacitor choices include aluminum electrolytic,
OS-Con, Tantalum and even ceramic dielectrics. An
aluminum electrolytic capacitor’s ESR value is related to
the case size with lower ESR available in larger case
sizes. However, the equivalent series inductance (ESL)
of these capacitors increases with case size and can
reduce the usefulness of the capacitor to high slew-rate
transient loading. Unfortunately, ESL is not a specified
parameter. Consult the capacitor manufacturer and/or
measure the capacitor’s impedance with frequency to
help select a suitable component.
OUTPUT INDUCTOR SELECTION
One of the parameters limiting the converter’s response
to a load transient is the time required to change the
inductor current. In a multi-phase converter, small
inductors reduce the response time with less impact to
the total output ripple current (as compared to
single-phase converters).
1.0
where L is the channel inductor value.
Find the intersection of the active channel curve and duty
cycle for your particular application. The resulting ripple
current multiplier from the y-axis is then multiplied by
the normalization factor, K NORM , to determine the total
output ripple current for the given application.
(EQ. 33)
INPUT CAPACITOR SELECTION
The important parameters for the bulk input
capacitors are the voltage rating and the RMS current
rating. For reliable operation, select bulk input
capacitors with voltage and current ratings above the
maximum input voltage and largest RMS current
required by the circuit. The capacitor voltage rating
should be at least 1.25 times greater than the
maximum input voltage. The input RMS current
required for a multi-phase converter can be
approximated with the aid of Figure 28. For a more
exact calculation of the input RMS current use
Equation 34:
I O ? ( D – D ) + I L , PP ? ------
0.8
I IN ( RMS ) =
2 2 2 D
12
(EQ. 34)
0.3
0.6
0.4
0.2
0.2
0
0
0.1
0.2
0.3
0.4
0.5
0.1
DUTY CYCLE (V O /V IN )
FIGURE 27. RIPPLE CURRENT vs DUTY CYCLE
I L,PP = 0
I L,PP = 0.5 x I O
The output inductor of each power channel controls the
ripple current. The control IC is stable for channel ripple
0
0
0.1
I L,PP = 0.75 x I O
0.2 0.3
0.4
0.5
current (peak-to-peak) up to twice the average current.
A single channel’s ripple current is approximated by
Equation 31:
DUTY CYCLE (V O /V IN )
FIGURE 28. NORMALIZED INPUT RMS CURRENT vs
DUTY CYCLE FOR A 2-PHASE CONVERTER
I L , PP = -------------------------------- × ----------------
F SW ? L V IN
V IN – V OUT V OUT
(EQ. 31)
As the input capacitors are responsible for sourcing the
AC component of the input current flowing into the upper
The current from multiple channels tend to cancel each
other and reduce the total ripple current. The total output
ripple current can be determined using the curve in
24
MOSFETs, their RMS current capacity must be sufficient
to handle the AC component of the current drawn by the
upper MOSFETs. Figure 28 can be used to determine the
input-capacitor RMS current function of duty cycle,
maximum sustained output current (I O ), and the ratio of
FN6352.2
October 27, 2009
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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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