参数资料
| 型号： | ISL95874IRUZ-T |
| 厂商： | Intersil |
| 文件页数： | 15/29页 |
| 文件大小： | 0K |
| 描述： | IC CTRLR PWM 1PHASE GPU 16UTQFN |
| 标准包装： | 3,000 |
| 应用： | 控制器，GPU 内核电源 |
| 输入电压： | 3.3 V ~ 25 V |
| 输出数： | 1 |
| 输出电压： | 0.5 V ~ 5 V |
| 工作温度： | -40°C ~ 100°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-UFQFN 裸露焊盘 |
| 供应商设备封装： | 16-UTQFN（2.6x1.8） |
| 包装： | 带卷 (TR) |
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ISL95874, ISL95875, ISL95876
Theory of Operation
The following sections will provide a detailed description of the
ISL95874, ISL95875, ISL95876 internal operation.
Power-On Reset
The IC is disabled until the voltage at the VCC pin has increased
above the rising power-on reset (POR) threshold voltage
V VCC_THR . The controller will disable when the voltage at the VCC
pin decreases below the falling POR threshold voltage V VCC_THF .
The POR detector has a noise filter of approximately 1μs.
Start-Up and Voltage-Step Operation for
ISL95875, ISL95876
When the voltage on the VCC pin has ramped above the rising
power-on reset voltage V VCC_THR , and the voltage on the EN pin
has increased above the rising enable threshold voltage V ENTHR ,
the SREF pin releases its discharge clamp and enables the
reference amplifier V SET . The soft-start current I SS is limited to
17μA and is sourced out of the SREF pin into the parallel RC
network of capacitor C SOFT and resistance R T . The resistance R T
is the sum of all the series connected R SET programming
resistors and is written as Equation 3:
Start-Up Timing
R T = R SET1 + R SET2 + … R SET ( n )
(EQ. 3)
t SS = – ( R T ? C SOFT ) ? LN ( 1 – ------------------------- )
V START-UP
I SS ? R T
t SS = -------------------------------------
t SS ? I SS
C SOFT = ---------------------
t VS = – ( R T ? C SOFT ) ? LN ( 1 – --------------------------------------- )
( V NEW – V OLD )
I VS ? R T
Once VCC has ramped above V VCC_THR , the controller will be
enabled by pulling the EN pin voltage above the input-high
threshold V ENTHR . In approximately 20μs, the voltage at the
SREF pin begins slewing to the designated VID set-point. The
converter output voltage at the FB feedback pin follows the
voltage at the SREF pin. During soft-start, the regulator always
operates in CCM until the soft-start sequence is complete.
Start-Up and Voltage-Step Operation for
ISL95874
When the voltage on the VCC pin has ramped above the rising
power-on reset voltage V VCC_THR , and the voltage on the EN pin
has increased above the rising enable threshold voltage V ENTHR ,
the SREF pin releases its discharge clamp, and enables the
reference amplifier V SET . The soft-start current I SS is limited to
17μA and is sourced out of the SREF pin and charges capacitor
C SOFT until V SREF equals V REF . The regulator controls the PWM
such that the voltage on the FB pin tracks the rising voltage on
the SREF pin. The elapsed time from when the EN pin is asserted
to when V SREF has charged C SOFT to V REF is called the soft-start
delay t SS , which is given by Equation 1:
V SREF ? C SOFT (EQ. 1)
I SS
Where:
- I SS is the soft-start current source at the 17μA limit
- V SREF is the buffered V REF reference voltage
The end of soft-start is detected by I SS tapering off when
capacitor C SOFT charges to V REF . The internal SSOK flag is set,
the PGOOD pin goes high, and diode emulation mode (DEM) is
enabled.
Choosing the C SOFT capacitor to meet the requirements of a
particular soft-start delay t SS is calculated using Equation 2:
(EQ. 2)
V SREF
Where:
- t SS is the soft-start delay
- I SS is the soft-start current source at the 17μA limit
- V SREF is the buffered V REF reference voltage
15
The voltage on the SREF pin rises as I SS charges C SOFT to the
voltage reference setpoint selected by the state of the VID inputs at
the time the EN pin is asserted. The regulator controls the PWM,
such that the voltage on the FB pin tracks the rising voltage on the
SREF pin. Once C SOFT charges to the selected setpoint voltage, the
I SS current source comes out of the 17μA current limit and decays
to the static value set by V SREF /R T . The elapsed time from when the
EN pin is asserted to when V SREF has reached the voltage reference
setpoint is the soft-start delay t SS , which is given by Equation 4:
(EQ. 4)
Where:
- I SS is the soft-start current source at the 17μA limit
- V START-UP is the setpoint reference voltage selected by the
state of the VID inputs at the time EN is asserted
- R T is the sum of the R SET programming resistors
The end of soft-start is detected by I SS tapering off when
capacitor C SOFT charges to the designated V SET voltage
reference setpoint. The SSOK flag is set, and the PGOOD pin goes
high.
The I SS current source changes over to the voltage-step current
source I VS , which has a current limit of ±85μA. Whenever the VID
inputs or the external setpoint reference programs a different
setpoint reference voltage, the I VS current source charges or
discharges capacitor C SOFT to that new level at ±85μA. Once
C SOFT charges to the selected setpoint voltage, the I VS current
source comes out of the 85μA current limit and decays to the
static value set by V SREF /R T . The elapsed time to charge C SOFT
to the new voltage is called the voltage-step delay t VS and is
given by Equation 5:
(EQ. 5)
Where:
- I VS is the ±85μA setpoint voltage-step current; positive when
V NEW > V OLD , negative when V NEW < V OLD
- V NEW is the new setpoint voltage selected by the VID inputs
- V OLD is the setpoint voltage that V NEW is changing from
- R T is the sum of the R SET programming resistors
FN7933.1
March 2, 2012
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ISL95875HRUZ-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| ISL95875IRUZ-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| ISL95901IRZ-T | 制造商:Intersil Corporation 功能描述:PMIC SOLUTION FOR PORTABLE 3.3V/5V SYSTEM POWER, 5X6 QFN, TR - Tape and Reel |
| ISL96017UIRT8Z | 功能描述:IC POT DGTL 50K OHM 8-TDFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数字电位器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 接片:256 电阻（欧姆）:100k 电路数:2 温度系数:标准值 35 ppm/°C 存储器类型:易失 接口:6 线串行（芯片选择，递增，增/减） 电源电压:2.6 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:14-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:14-TSSOP 包装:带卷 (TR) |
| ISL96017UIRT8Z-T | 功能描述:IC XDCP 128-TAP 50KOHM 8-TDFN RoHS:是 类别:集成电路 (IC) >> 数据采集 - 数字电位器 系列:- 产品培训模块:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 标准包装:2,500 系列:- 接片:256 电阻（欧姆）:100k 电路数:2 温度系数:标准值 35 ppm/°C 存储器类型:易失 接口:6 线串行（芯片选择，递增，增/减） 电源电压:2.6 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:14-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:14-TSSOP 包装:带卷 (TR) |
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