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| 型号： | ISL6558IR |
| 厂商： | Intersil |
| 文件页数： | 14/16页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM 20-QFN |
| 标准包装： | 60 |
| PWM 型： | 控制器 |
| 输出数： | 1 |
| 频率 - 最大： | 1.5MHz |
| 占空比： | 75% |
| 电源电压： | 4.75 V ~ 5.25 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： | 20-VQFN 裸露焊盘 |
| 包装： | 管件 |
ISL6558
The total output ripple current can be determined from the
curves in Figure 10. They provide 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.
value found and the result is the RMS input current whi c h
must be supported by the input capacitors.
0.5
K NORM = ---------------------
V OUT
LxF SW
where L is the channel inductor value.
(EQ. 11)
0.4
0.3
SINGLE
CHANNEL
2 CHANNEL
1.0
0.2
0.8
0.6
SINGLE
CHANNEL
0.1
4 CHANNEL
3 CHANNEL
2 CHANNEL
0
0
0.1
0.2
0.3
0.4
0.5
0.4
0.2
0
3 CHANNEL
4 CHANNEL
DUTY CYCLE (V O /V IN )
FIGURE 11. CURRENT MULTIPLIER vs DUTY CYCLE
MOSFET SELECTION AND CONSIDERATIONS
The ISL6558 requires two N-Channel power MOSFETs per
0
0.1
0.2 0.3
DUTY CYCLE (V O /V IN )
0.4
0.5
active channel or more if parallel MOSFETs are employed.
These MOSFETs should be selected based upon r DS(ON) ,
FIGURE 10. RIPPLE CURRENT vs DUTY CYCLE
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.
total gate charge, and thermal management requirements.
In high-current PWM applications, the MOSFET power
dissipation, package selection and heatsink are the
dominant design factors. The power dissipation includes two
loss components; conduction loss and switching loss. These
losses are distributed between the upper and lower
MOSFETs according to duty cycle of the converter (see the
D I TOTAL = K NORM xK CM
(EQ. 12)
equations below). The conduction losses are the main
component of power dissipation for the lower MOSFETs, Q2
I O × r DS ( ON ) × V OUT
I O × V IN × t SW × F SW
P UPPER = ------------------------------------------------------------ + ----------------------------------------------------------
V IN
INPUT CAPACITOR SELECTION
Use a mix of input bypass capacitors to control the voltage
overshoot across the MOSFETs. Use ceramic capacitors for
the high frequency decoupling and bulk capacitors to supply
the RMS current. Small ceramic capacitors can be placed
very close to the upper MOSFET to suppress the voltage
induced in the parasitic circuit impedances.
Two important parameters to consider when selecting the
bulk input capacitor are the voltage rating and the RMS
current rating. For reliable operation, select a bulk capacitor
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 and a voltage rating of 1.5
times is a conservative guideline. The RMS current
requirement for a converter design can be approximated with
the aid of Figure 11. Follow the curve for the number of active
channels in the converter design. Next determine the duty
and Q4 of Figure 1. Only the upper MOSFETs, Q1 and Q3
have significant switching losses, since the lower device turn
on and off into near zero voltage.
The following equations assume linear voltage-current
transitions and do not model power loss due to the reverse-
recovery of the lower MOSFETs body diode. The gate-
charge losses are dissipated in the HIP660x drivers and
don’t heat the MOSFETs. However, large gate-charge
increases the switching time, t SW which increases the upper
MOSFET switching losses. Ensure that both MOSFETs are
within their maximum junction temperature at high ambient
temperature by calculating the temperature rise according to
package thermal-resistance specifications. A separate
heatsink may be necessary depending upon MOSFET
power, package type, ambient temperature and air flow.
2
2
(EQ. 13)
I O × r DS ( ON ) × ( V IN – V OUT )
P LOWER = ---------------------------------------------------------------------------------
cycle for the converter and find the intersection of this value
and the active channel curve. Find the corresponding y-axis
value, which is the current multiplier. Multiply the total full load
output current, not the channel value, by the current multiplier
14
2
V IN
(EQ. 14)
FN9027.12
June 21, 2005
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| ISL6558IR-T | 功能描述:IC REG CTRLR BUCK PWM 20-QFN 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:4,000 系列:- PWM 型:电压模式 输出数:1 频率 - 最大:1.5MHz 占空比:66.7% 电源电压:4.75 V ~ 5.25 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:40-VFQFN 裸露焊盘 包装:带卷 (TR) |
| ISL6558IRZ | 功能描述:IC REG CTRLR BUCK PWM 20-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) |
| ISL6558IRZA | 功能描述:IC REG CTRLR BUCK PWM 20-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) |
| ISL6558IRZA-T | 功能描述:IC REG CTRLR BUCK PWM 20-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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