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| 型号： | ISL8022EVAL1Z |
| 厂商： | Intersil |
| 文件页数： | 14/18页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD 1 FOR ISL8022 |
| 标准包装： | 1 |
| 系列： | * |
ISL8022
Theory of Operation
The ISL8022 is a dual 2A/1.7A step-down switching regulator
optimized for battery-powered or mobile applications. The
regulator operates at 2.25MHz fixed switching frequency under
heavy load condition to allow small external inductor and
capacitors to be used for minimal printed-circuit board (PCB)
area. At light load, the regulator reduces the switching frequency,
unless forced to the fixed frequency, to minimize the switching
loss and to maximize the battery life. The two channels are 180°
out-of-phase operation. The quiescent current when the outputs
are not loaded is typically only 40μA. The supply current is
typically only 6.5μA when the regulator is shut down.
PWM Control Scheme
Pulling the SYNC pin LOW (<0.4V) forces the converter into PWM mode
in the next switching cycle regardless of output current. Each of the
channels of the ISL8022 employs the current-mode pulse-width
modulation (PWM) control scheme for fast transient response and
The current loop consists of the oscillator, the PWM comparator COMP,
current sensing circuit, and the slope compensation for the current loop
stability. The current sensing circuit consists of the resistance of the
P-channel MOSFET when it is turned on and the current sense amplifier
CSA1 (or CSA2 on Channel 2). The gain for the current sensing circuit is
typically 0.32V/A. The control reference for the current loops comes
from the error amplifier EAMP of the voltage loop.
The PWM operation is initialized by the clock from the oscillator.
The P-channel MOSFET is turned on at the beginning of a PWM
cycle and the current in the MOSFET starts to ramp up. When the
sum of the current amplifier CSA1 (or CSA2) and the
compensation slope (0.9V/μs) reaches the control reference of the
current loop, the PWM comparator COMP sends a signal to the
PWM logic to turn off the P-MOSFET and to turn on the N-channel
MOSFET. The N-MOSFET stays on until the end of the PWM cycle.
Figure 44 shows the typical operating waveforms during the PWM
operation. The dotted lines illustrate the sum of the compensation
ramp and the current-sense amplifier CSA_ output.
The output voltage is regulated by controlling the reference
voltage to the current loop. The bandgap circuit outputs a 0.6V
reference voltage to the voltage control loop. The feedback signal
comes from the V FB pin. The soft-start block only affects the
operation during the start-up and will be discussed separately
shortly. The error amplifier is a transconductance amplifier that
converts the voltage error signal to a current output. The voltage
loop is internally compensated with the 27pF and 250k Ω RC
network. The maximum EAMP voltage output is precisely
clamped to 1.8V.
14
V EAMP
V CSA
DUTY
CYCLE
I L
V OUT
FIGURE 44. PWM OPERATION WAVEFORMS
SKIP Mode
Pulling the SYNC pin HIGH (>1.5V) enable the converter into PFM
mode at low load. The ISL8022 enters a pulse-skipping mode at
light load to minimize the switching loss by reducing the switching
frequency. Figure 45 illustrates the skip-mode operation. A
zero-cross sensing circuit shown in block diagram monitors the
N-MOSFET current for zero crossing. When 16 consecutive cycles of
the N-MOSFET crossing zero are detected, the regulator enters the
skip mode. During the 16 detecting cycles, the current in the
inductor is allowed to become negative. The counter is reset to zero
when the current in any cycle does not cross zero.
Once the skip mode is entered, the pulse modulation starts being
P-MOSFET is turned on at the clock and turned off when its current
reaches the threshold of 600mA. As the average inductor current in
each cycle is higher than the average current of the load, the output
voltage rises cycle over cycle. When the output voltage reaches
1.5% above the nominal voltage, the P-MOSFET is turned off
immediately. Then the inductor current is fully discharged to zero
and stays at zero. The output voltage reduces gradually due to the
load current discharging the output capacitor. When the output
voltage drops to the nominal voltage, the P-MOSFET will be turned
on again at the clock, repeating the previous operations.
The regulator resumes normal PWM mode operation when the
output voltage drops 1.5% below the nominal voltage.
Synchronization Control
The frequency of operation can be synchronized up to 8MHz by
an external signal applied to the SYNC pin. The 1st falling edge
on the SYNC triggered the rising edge of the PWM ON pulse of
Channel 1. The 2nd falling edge of the SYNC triggers the rising
edge of the PWM ON pulse of the Channel 2. This process
alternates indefinitely allowing 180° output phase operation
between the two channels.The internal frequency will take
control when the divided external sync is lower than 2.25MHz.
The falling edge on the SYNC triggers the rising edge of the PWM
ON pulse.
FN7650.3
March 14, 2013
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| ISL8022IRZ-T | 功能描述:IC REG BUCK SYNC ADJ DL 12DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:两者兼有 输出数:1 输出电压:5V，1 V ~ 10 V 输入电压:3.5 V ~ 28 V PWM 型:电流模式 频率 - 开关:220kHz ~ 1MHz 电流 - 输出:600mA 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:16-SSOP（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:16-QSOP |
| ISL8022IRZ-T7A | 功能描述:IC REG BUCK SYNC ADJ DL 12DFN RoHS:是 类别:集成电路 (IC) >> PMIC - 稳压器 - DC DC 开关稳压器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 类型:降压（降压） 输出类型:两者兼有 输出数:1 输出电压:5V，1 V ~ 10 V 输入电压:3.5 V ~ 28 V PWM 型:电流模式 频率 - 开关:220kHz ~ 1MHz 电流 - 输出:600mA 同步整流器:无 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:16-SSOP（0.154"，3.90mm 宽） 包装:带卷 (TR) 供应商设备封装:16-QSOP |
| ISL8023 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:3A/4A Low Quiescent Current High Efficiency Synchronous Buck Regulator |
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