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参数资料
| 型号： | ISL8105BEVAL2Z |
| 厂商： | Intersil |
| 文件页数： | 2/11页 |
| 文件大小： | 0K |
| 描述： | EVALUATION BOARD FOR ISL8105B |
| 标准包装： | 1 |
| 主要目的： | DC/DC，步降 |
| 输出及类型： | 1，非隔离 |
| 输出电压： | 1.8V |
| 电流 - 输出： | 15A |
| 输入电压： | 9.6 ~ 14.4V |
| 稳压器拓扑结构： | 降压 |
| 频率 - 开关： | 300kHz |
| 板类型： | 完全填充 |
| 已供物品： | 板 |
| 已用 IC / 零件： | ISL8105B |
Application Note 1288
The total power loss in MOSFET consists of conduction loss
and switching loss, as shown in Equation 5:
Hence, the required ON-resistance of the high-side MOSFET is
7.3m Ω . Infineon’s BSC080N03LS is selected. The conduction
P HFET ( cond ) = I H ( RMS ) ? r DS ( ON )
(EQ. 11)
P MOSFET ( TOT ) = P cond + P sw
In this relatively small duty cycle design, the low-side
(EQ. 5)
loss in the high-side MOSFET is calculated using Equation 11:
2
= 0.27W
HFET
P HFET ( SW ) = --- ? I O ? V IN ? t tr ? F SW + --- ? C OSS ? V IN ? F SW
MOSFET conducts current most of the time. To optimize the
converter efficiency, select the high-side MOSFET with low
gate charge for fast switching transition and low-side
MOSFET with low r DS(ON) .
The switching loss in the high-side MOSFET can be
approximated using Equation 12:
1 1 2
2 2
To achieve the target efficiency, the budget power losses in
= 0.17W
(EQ. 12)
high-side and low-side MOSFETs are 0.5W and 1W,
respectively.
LOW-SIDE MOSFET SELECTION
The low-side MOSFET’s RMS current is approximated in
where t tr is the combined ON and OFF MOSFET transition
times.
The total power dissipation in high-side MOSFET is shown in
Equation 13:
Equation 6:
P HFET ( TOT ) = 0.44W
(EQ. 13)
I L ( RMS ) = I OUT ? 1 – D ? 1 + ------ ? ? ------------- ? ≈ 13.9A
1 ? Δ I L ? 2
12 ? I OUT ?
(EQ. 6)
Overcurrent Protection Setting
Therefore, the ON-resistance of the low-side MOSFET must
be less than 5m Ω . Infineon’s BSC030N03LS is employed in
the ISL8105BEVAL1Z, ISL8105BEVAL2Z evaluation board.
The conduction loss in the low-side MOSFET is calculated
using Equation 7:
The overcurrent function protects the converter from a shorted
output by using the low-side MOSFET’s r DS(ON) to monitor
the current. A resistor, R BSOC , programs the overcurrent trip
level. If overcurrent is detected, the output immediately shuts
off, it cycles the soft-start function in a hiccup mode (2 dummy
soft-start time-outs, then up to one real one) to provide fault
P LFET ( cond ) = I L ( RMS ) ? r DS ( ON )
2
LFET
= 0.58W
(EQ. 7)
protection. If the shorted condition is not removed, this cycle
will continue indefinitely.
The switching loss in the low-side MOSFET is dominated by
the loss in body diode which can be calculated using
The overcurrent function will trip at a inductor current (I trip ) is
determined using Equation 14:
I trip = ---------------------------------------------------------
Equation 8:
P diode = I O ? t D ? V F ? F SW = 0.3W
(EQ. 8)
2 ? I OCSET ? R BSOC
r DS ( ON )
(EQ. 14)
Where t D is the total dead time in each switching period
(~60μs) and V F is the forward voltage drop of MOSFET’s
body diode.
The total power dissipation in the low-side MOSFET is
calculated using Equation 9:
where I OCSET is the internal 21.5μA (typ.) OCSET current
source.
The OC trip point varies mainly due to the MOSFET’s r DS(ON)
variations. To avoid overcurrent tripping in the normal operating
load range, calculate the R BSOC resistor from Equation 14
P LFET ( TOT ) = 0.88W
(EQ. 9)
using:
1. The maximum r DS(ON) at the highest junction temperature.
HIGH-SIDE MOSFET SELECTION
For the high-side MOSFET selection, first we assume that
the conduction loss and the switching loss contribute evenly
to the total power dissipation.
The high-side MOSFET’s RMS current is approximated
using Equation 10:
2. The minimum I OCSET from the specification table of the
datasheet.
Determine I trip for I trip > I OUT(MAX) + ( Δ I)/2, where Δ I is the
output inductor ripple current.
I H ( rms ) = I OUT ? D ? 1 + ------ ? ? ------------- ? ≈ 5.85A
1 ? Δ I L ? 2
12 ? I OUT ?
2
(EQ. 10)
AN1288.1
October 30, 2008
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| ISL8105BIBZ | 功能描述:IC REG CTRLR BUCK 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) |
| ISL8105BIBZ-T | 功能描述:IC REG CTRLR BUCK 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) |
| ISL8105BIRZ | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN 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) |
| ISL8105BIRZ-T | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN 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) |
| ISL8105CRZ | 功能描述:IC REG CTRLR BUCK PWM VM 10-DFN 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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