- 您现在的位置：买卖IC网 > PDF目录17320 > ISL8088EVAL1Z (Intersil)EVAL BOARD 1 FOR ISL8088 PDF资料下载
参数资料
| 型号： | ISL8088EVAL1Z |
| 厂商： | Intersil |
| 文件页数： | 14/18页 |
| 文件大小： | 0K |
| 描述： | EVAL BOARD 1 FOR ISL8088 |
| 标准包装： | 1 |
| 系列： | * |
ISL8088
Theory of Operation
The ISL8088 is a dual 800mA step-down switching regulator
optimized for battery-powered or mobile applications. The
regulator operates at 2.25MHz fixed switching frequency under
heavy load conditions 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 in-
phase operation. The quiescent current when the outputs are not
loaded is typically only 30μA. 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 ISL8088 employ the current-mode
pulse-width modulation (PWM) control scheme for fast transient
response and pulse-by-pulse current limiting shown in the “Block
Diagram” on page 13. 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
0.285V/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 (0.33V/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 43 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
PWM
CLOCK
8 CYCLES
I L
0
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 200k ? RC
network. The maximum EAMP voltage output is precisely
clamped to 0.8V.
V EAMP
V CSA
DUTY
CYCLE
I L
V OUT
FIGURE 43. PWM OPERATION WAVEFORMS
SKIP Mode
Pulling the SYNC pin HIGH (>2.0V) forces the converter into PFM
mode. The ISL8088 enters a pulse-skipping mode at light load to
minimize the switching loss by reducing the switching frequency.
Figure 44 illustrates the skip-mode operation. A zero-cross sensing
circuit shown in the “Block Diagram” on page 13 monitors the N-
MOSFET current for zero crossing. When 8 consecutive cycles of
the N-MOSFET crossing zero are detected, the regulator enters the
skip mode. During the 8 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
controlled by the SKIP comparator shown in the “Block Diagram”
on page 13. Each pulse cycle is still synchronized by the PWM
clock. The P-MOSFET is turned on at the clock and turned off
when its current reaches the threshold of 250mA. 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
PFM
PFM CURRENT LIMIT
LOAD CURRENT
NOMINAL +1.5%
V OUT
NOMINAL
FIGURE 44. SKIP MODE OPERATION WAVEFORMS
14
FN6858.2
May 26, 2011
相关PDF资料 |
PDF描述 |
|---|---|
| GBC08DCST | CONN EDGECARD 16POS DIP .100 SLD |
| GBC13DCAN | CONN EDGECARD 26POS R/A .100 SLD |
| ISL8120EVAL3Z | EVALUATION BOARD FOR ISL8120 |
| ISL6455AEVAL1Z | EVALUATION BOARD FOR ISL6455A |
| ISL6455EVAL1Z | EVALUATION BOARD FOR ISL6455 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL8088EVAL2Z | 功能描述:EVAL BAORD FOR ISL8088 RoHS:是 类别:编程器，开发系统 >> 评估板 - DC/DC 与 AC/DC（离线）SMPS 系列:* 产品培训模块:Obsolescence Mitigation Program 标准包装:1 系列:True Shutdown™ 主要目的:DC/DC，步升 输出及类型:1，非隔离 功率 - 输出:- 输出电压:- 电流 - 输出:1A 输入电压:2.5 V ~ 5.5 V 稳压器拓扑结构:升压 频率 - 开关:3MHz 板类型:完全填充 已供物品:板 已用 IC / 零件:MAX8969 |
| ISL8088IRZ | 功能描述:IC REG BUCK SYNC ADJ 0.8A 10DFN 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 |
| ISL8088IRZ-T | 功能描述:IC REG BUCK SYNC ADJ 0.8A 10DFN 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 |
| ISL8088IRZ-T7A | 功能描述:直流/直流开关转换器 DUAL 2.25MHZ 800MA SYNC REG - 3X3 RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT |
| ISL8101 | 制造商:INTERSIL 制造商全称:Intersil Corporation 功能描述:Two-Phase Multiphase Buck PWM Controller with Integrated MOSFET Drivers |
发布紧急采购，3分钟左右您将得到回复。