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参数资料
| 型号： | MAX1762EUB+ |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/20页 |
| 文件大小： | 0K |
| 描述： | IC REG CTRLR BUCK PWM CM 10-UMAX |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 50 |
| PWM 型： | 电流模式 |
| 输出数： | 1 |
| 频率 - 最大： | 328kHz |
| 电源电压： | 5 V ~ 20 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： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 包装： | 管件 |
High-Efficiency, 10-Pin μMAX, Step-Down
Controllers for Notebooks
( )
2.55 μ s
( )
( )
Overdriving the VL regulator with an external 5V supply
also increases the MAX1762/MAX1791s’ efficiency.
The MAX1762/MAX1791 include an input undervoltage
lockout (UVLO) circuit that prevents the device from
switching until VL > 4.4V (max). UVLO ensures there is
a sufficient drive for the external MOSFETs, prevents
the high-side MOSFET from being turned on for near
100% duty cycle, and keeps the output in regulation.
Voltage Reference (REF)
The 2V reference (REF) is accurate to ±1% over tem-
perature, making REF useful as a precision system ref-
erence. Bypass REF to GND with a 0.1μF (min) ceramic
capacitor. REF can supply up to 50μA for external
loads. However, if tight-accuracy specs for either V OUT
or REF are essential, avoid loading REF. Loading slight-
ly reduces the main output voltage by an amount that
tracks the reference-voltage load regulation error.
Free-Running Constant On-Time PWM
Controller with Input Feed-Forward
The PWM control architecture is a quasi-fixed-frequen-
cy constant on-time current-mode type with voltage
feed-forward. This architecture relies on the output rip-
ple voltage to provide the PWM ramp signal; thus, the
adjustable 0.5μs (max) minimum off-time. Worst-case
dropout performance is determined by the minimum
on-time spec. The worst-case duty factor limit is:
t ON MIN
= = 84%
t ON MIN + t OFF MAX 2.55 μ s+0.5 μ s
with V BATT = 6V and V OUT = 5V. Therefore, with IR volt-
age drops in the loop included, the minimum input volt-
age to achieve V OUT = 5V is about 6.1V, using the
step-down transfer function equation for duty cycle (DC
= V OUT /V IN ). Typical units exhibit better performance.
Note that transient response is somewhat degraded
near dropout, and the circuit may need additional bulk
output capacitance to support fast load changes.
Automatic Pulse-Skipping Switchover
This PWM control algorithm automatically switches over
to pulse-skipping operation at light loads. The
MAX1762/MAX1791 truncates the low-side switch’s on-
time when the inductor current drops to zero. The load
current level at which pulse-skipping/PWM crossover
occurs is equal to 1/2 the peak-to-peak ripple current,
which is a function of the inductor value (Figure 6):
?
?
? ?
output filter capacitor’s ESR acts as a feedback resis-
tor. The control algorithm is very simple. The high-side
switch on-time is determined solely by a one-shot
I LOAD(SKIP) =
K × V OUT
2L
? V VP - V OUT ?
V VP
( V OUT + 0.075V )
whose period is inversely proportional to input voltage
and directly proportional to output voltage. There is
another one-shot that sets a minimum amount of off-
time (500ns max). The on-time one-shot triggers when
all of the following conditions are met: the error com-
parator is low, the low-side switch current is below the
current-limit threshold, and the minimum off-time one-
shot has timed out.
On-Time One-Shot
The on-time of the one-shot is inversely proportional to
the battery voltage as measured by the VP input, and
directly proportional to the output voltage sensed at
OUT:
t ON = K ×
V BATT
where K is internally fixed at 3.349μs, and 0.075V is a
factor that accounts for the expected drop across the
The inductor current is never allowed to go negative. If
the output voltage is above its regulation point and the
inductor current reaches zero, the low-side driver is
switched off. Once the output voltage falls below its
regulation point, the high-side driver is switched on.
This causes a dead time in between when the high-
side and low-side drivers are on, skipping pulses and
resulting in the switching frequency slowing at light
loads, thereby improving efficiency.
MOSFET Gate Drivers
The DH and DL drivers are optimized for driving moder-
ate-size power MOSFETs. This is consistent with the
low duty factor seen in the notebook CPU environment
where a large V BATT - V OUT differential exists. The high-
side driver (DH) is rated for 0.6A source/sink capability
and swings from VP to GND. The low-side driver (DL) is
Table 3. Operating Frequency
synchronous switch. This arrangement maintains a
switching frequency that is nearly constant as V BATT ,
I LOAD , and V OUT are changed. Table 3 shows the oper-
ating frequency range for the MAX1762/MAX1791.
DEVICE
MAX1762/MAX1791
K
( μ s)
3.349
MIN
(kHz)
268.7
TYP
(kHz)
298.5
MAX
(kHz)
328
Note that the output voltage adjust range for continu-
ous-conduction operation is restricted by the non-
12
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1762EUB+ | 功能描述:DC/DC 开关控制器 Step-Down Controller for Notebooks RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1762EUB+T | 功能描述:DC/DC 开关控制器 Step-Down Controller for Notebooks RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1762EUB-T | 功能描述:DC/DC 开关控制器 RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
| MAX1763EEE | 功能描述:直流/直流开关转换器 1.5A Low-Noise 1MHz Step-Up 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 |
| MAX1763EEE+ | 功能描述:直流/直流开关转换器 1.5A Low-Noise 1MHz Step-Up 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 |
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