参数资料
| 型号： | ISL8011IRZ-T |
| 厂商： | Intersil |
| 文件页数： | 8/10页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK SYNC ADJ 1.2A 10DFN |
| 标准包装： | 6,000 |
| 类型： | 降压（降压） |
| 输出类型： | 可调式 |
| 输出数： | 1 |
| 输出电压： | 0.8 V ~ 5.5 V |
| 输入电压： | 2.7 V ~ 5.5 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 1.6MHz |
| 电流 - 输出： | 1.2A |
| 同步整流器： | 是 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-VFDFN 裸露焊盘 |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 10-DFN（3x3） |
ISL8011
a level that the ISL8011 can no longer maintain the
TABLE 1. OUTPUT CAPACITOR VALUE vs V OUT
regulation at the output, the regulator completely turns on
the P-MOSFET. The maximum drop out voltage under the
100% duty-cycle operation is the product of the load current
and the ON-resistance of the P-MOSFET.
Enable
The enable (EN) input allows user to control the turning on
or off the regulator for purposes such as power-up
sequencing. The the regulator is enabled, there is typically a
300μs delay for waking up the bandgap reference. Then the
soft start-up begins. When the regulator is disabled, the
V OUT
0.8V
1.2V
1.6V
1.8V
2.5V
3.3V
3.6V
C OUT
10μF
10μF
10μF
10μF
10μF
6.8μF
4.7μF
L
1.0μH~2.2μH
1.2μH~2.2μH
1.8μH~2.2μH
1.8μH~3.3μH
1.8μH~3.3μH
1.8μH~4.7μH
1.8μH~4.7μH
P-MOSFET is turned off immediately and the N-MOSFET is
V O ? ? 1 – --------- ? (EQ. 1)
L ? f S
turned on.
Thermal Shut Down
The ISL8011 has built-in thermal protection. When the
internal temperature reaches +150°C, the regulator is
completely shut down. As the temperature drops to +130°C,
the ISL8011 resumes operation by stepping through a soft
start-up.
V CC By-Passing
The V CC is voltage is the supply to the internal control circuit
and is derived from the PVIN pin. An internal 5 Ω resistor
connects the two pins and also serves as an filtering resistor.
An external 0.1μF ceramic capacitor is recommended to
by-pass the V CC supply.
Applications Information
Output Inductor and Capacitor Selection
To consider state steady and transient operation, ISL8011
typically uses a 1.8μH output inductor. Higher or lower
inductor values can be used to optimize the total converter
system performance. For example, for higher output voltage
3.3V application, in order to decrease the inductor current
ripple and output voltage ripple, the output inductor value
can be increased as shown in Table 1. The inductor ripple
current can be expressed as shown in Equation 1:
? V O ?
? V IN ?
Δ I = ---------------------------------------
The inductor ’s saturation current rating needs be at least
larger than the peak current. The maximum peak current of
ISL8011 is 2.1A. The saturation current needs be over 2.1A
for maximum output current application.
In Table 1, the minimum output capacitor value is given for
different output voltage to make sure the whole converter
system stable. Due to the limitation on power dissipation
when the regulator disable and discharge output capacitor,
there is the maximum output capacitor value. The maximum
output capacitor value is variable with the output voltage.
The plot curve is shown in Figure 13.
600
505
410
315
220
125
30
0.8 1.27 1.73 2.2 2.67 3.13 3.6
OUTPUT VOLTAGE (V)
FIGURE 13. THE MAXIMUM CAP vs THE OUTPUT VOLTAGE
Input Capacitor Selection
The main functions for the input capacitor are to provide
decoupling of the parasitic inductance and to provide filtering
function to prevent the switching current flowing back to the
supply rail. A 10μF X5R or X7R ceramic capacitor is a good
starting point for the input capacitor selection.
Output Voltage Setting Resistor Selection
The resistors R 2 and R 3 shown in Figure 10 set the output
voltage for the adjustable version. The output voltage can be
calculated by using Equation 2:
V O = 0.8 ? ? 1 + ------- ?
ISL8011 uses internal compensation network and the output
capacitor value is dependent on the output voltage. The
? R 2 ?
? R 3 ?
(EQ. 2)
ceramic capacitor is recommended to be X5R or X7R. The
recommended minimum output capacitor values are shown
in Table 1.
8
where the 0.8V is the reference voltage. To minimize the
accuracy impact on the output voltage, select the R 2 and R 3
no larger than 100k Ω .
FN9254.2
August 4, 2009
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