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| 型号： | MAX1993ETG+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 20/36页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 24-TQFN |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 75 |
| 系列： | Quick-PWM™ |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 600kHz |
| 占空比： | 100% |
| 电源电压： | 4.5 V ~ 5.5 V |
| 降压： | 是 |
| 升压： | 无 |
| 回扫： | 无 |
| 反相： | 无 |
| 倍增器： | 无 |
| 除法器： | 无 |
| Cuk： | 无 |
| 隔离： | 无 |
| 工作温度： | -40°C ~ 85°C |
| 封装/外壳： | 24-WFQFN 裸露焊盘 |
| 包装： | 管件 |
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Quick-PWM Step-Down Controllers with Inductor
Saturation Protection and Dynamic Output Voltages
Δ V ILIM = ? ? A B ? I ILIM ( LSAT )
In forced-PWM mode, the MAX1992/MAX1993 also
implement a negative current limit to prevent excessive
reverse inductor currents when V OUT is sinking current.
The negative current-limit threshold is set to approxi-
mately 120% of the positive current limit and tracks the
positive current limit when ILIM is adjusted.
The current-limit threshold is adjusted with an external
resistor-divider at ILIM. A 2μA to 20μA divider current is
recommended for accuracy and noise immunity. The
current-limit threshold adjustment range is from 25mV
to 200mV. In the adjustable mode, the current-limit
threshold voltage is precisely 1/10th the voltage seen at
ILIM. The threshold defaults to 50mV when ILIM is con-
nected to V CC . The logic threshold for switchover to the
50mV default value is approximately V CC - 1V.
Carefully observe the PC board layout guidelines to
ensure that noise and DC errors do not corrupt the dif-
ferential current-sense signals seen by CSP and CSN.
Place the IC close to the sense resistor with short,
direct traces, making a Kelvin-sense connection to the
current-sense resistor.
Inductor Saturation Limit
The LSAT connection selects an upper current-sense
limit as the inductor saturation threshold or disables the
inductor saturation protection feature altogether (LSAT
= GND). When enabled, the inductor saturation thresh-
old is set as a multiple of the positive valley current-limit
threshold (Table 4) and tracks the valley current limit
This reduces the voltage on ILIM by Δ V ILIM where:
? R × R ?
? R A + R B ?
where I ILIM(LSAT) is 6μA ILIM saturation fault sink cur-
rent (see the Electrical Characteristics table). When
using the default 50mV valley current-limit threshold
(ILIM = V CC ), the ILIM saturation fault sink current does
not lower the current-limit threshold (see Figure 2).
If the inductor current remains below the saturation
threshold during the next cycle, the ILIM discharge cur-
rent is disabled, and the ILIM voltage returns to its orig-
inal set point. The inductor should not remain in
saturation once the controller reduces the valley current
limit. However, if the inductor remains in saturation, the
output voltage may drop low enough to trip the under-
voltage fault protection (UVP enabled), causing the
MAX1992/MAX1993 to shut down and latch off. Adding
a capacitor from ILIM to GND slows the ILIM voltage
change by the time constant τ = (R A //R B ) x C ILIM . A
suitable time constant is between 5 to 10 switching
cycles. If the inductor saturation occurs only during a
short load transient, the time constant allows the power
supply to recover before the output voltage drops
below the output undervoltage threshold.
Set Δ V ILIM to be at least 30% (LIR) of the ILIM set volt-
age. Calculate R A and R B using the equations below:
I ILIM ( LSAT ) ? V ILIM ( SET ) ?
? V ILIM ( SET ) ?
when ILIM is adjusted. The inductor saturation thresh-
old should be selected to give sufficient headroom
above the peak inductor current so switching noise
does not accidentally trip the saturation protection.
Selecting too high a threshold can cause an inductor
saturation to go undetected. For an inductor with a low
LIR (the ratio of the inductor ripple current to the
designed maximum load current) of approximately
R A =
? Δ V ILIM ?
V REF ? Δ V ILIM ?
? ?
with ? ? set at 30 %
?
?
? 1 ?
20%, the lowest saturation threshold of 1.5 x I LIM(VAL)
(LSAT = REF) may be acceptable. When using an
inductor with a higher LIR, increase the inductor satura-
tion threshold accordingly.
R B =
R A
V REF
? V ILIM ( SET )
?
?
When inductor saturation is enabled, the MAX1992/
MAX1993 continuously monitor the inductor current
through the voltage across the current-sense resistor.
When the inductor saturation threshold is exceeded, the
MAX1992/MAX1993 immediately turn off the high-side
gate driver and enable a 6μA discharge current on ILIM
Inductor saturation works best using a current-sense
resistor in series with the inductor. A low-side current-
sense resistor configuration can sense the saturation
Table 4. LSAT Configuration Table
(Figure 4) at the beginning of the next DH on-time.
LSAT
V CC
Open
REF
GND
INDUCTOR SATURATION THRESHOLD
2.00 × I LIM(VAL)
1.75 × I LIM(VAL)
1.50 × I LIM(VAL)
Disabled
20
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1993ETG+ | 功能描述:电压模式 PWM 控制器 Step-Down w/Inductor RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1993ETG+T | 功能描述:电压模式 PWM 控制器 Step-Down w/Inductor RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1993ETG+TG40 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
| MAX1993ETG-T | 功能描述:电压模式 PWM 控制器 RoHS:否 制造商:Texas Instruments 输出端数量:1 拓扑结构:Buck 输出电压:34 V 输出电流: 开关频率: 工作电源电压:4.5 V to 5.5 V 电源电流:600 uA 最大工作温度:+ 125 C 最小工作温度:- 40 C 封装 / 箱体:WSON-8 封装:Reel |
| MAX1993EVKIT | 制造商:Maxim Integrated Products 功能描述:EVALUATION KIT FOR THE MAX1992 MAX1993 - Bulk |
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