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参数资料
| 型号： | MAX8939EWV+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 24/45页 |
| 文件大小： | 0K |
| 描述： | IC PWR MGMT HANDSETS 30WLP |
| 标准包装： | 2,500 |
| 应用： | 充电泵，无线设备 |
| 输入电压： | 2.9 V ~ 5.5 V |
| 输出数： | 7 |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | * |
| 封装/外壳： | * |
| 供应商设备封装： | * |
| 包装： | * |
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MAX8939/MAX8939A/MAX8939B
System Power Management
for Mobile Handset
Soft-Start OUT2
From shutdown, once LED1 or LED2 is enabled through
the I 2 C interface, the step-up converter prepares for
soft-start. C COMP2 is quickly pulled to 1V by an internal
pullup clamp. Since the LED_ feedback node voltage
is less than the regulation threshold (0.35V typ), 40 F A
current is sourced from the error amplifier and further
charges C COMP2 . Once V COMP2 reaches 1.25V, the
step-up converter starts switching at a reduced duty
cycle. As V COMP2 rises, the step-up converter duty
cycle increases.
When V LED1 or V LED2 reaches 0.35V (typ), the error
amplifier stops sourcing current to C COMP2 , soft-start
ends, and the control loop achieves regulation as V LED_
settles. The V COMP2 where the step-up converter exits
soft-start depends on the load. A 2.5V upper limit to
V COMP2 is imposed to aid in transient recovery and to
allow maximum output for low input voltages. C COMP2
is discharged to ground through a 20k I internal resistor
whenever the step-up converter is turned off, allowing
the device to reinitiate soft-start when it is enabled.
LED1 and LED2 Current Regulators
Each current regulator drives a series string of LEDs. The
maximum number of LEDs depends of maximum forward
voltage of the LEDs at the maximum desired current. The
total forward voltage of the LED string must be below
27.65V. The LED current is independently programmed
using the I 2 C interface from 50 F A to 25.25mA with a 128-
step logarithmic dimming scheme.
Ramp-Up/-Down
The ICs’ LED current regulators provide ramp- up and
ramp-down functionality for smooth transitions between
different brightness settings. A controlled ramp is used
when the LED current level is changed, and when the
LEDs are enabled or disabled. LED1 and LED2 have
individual ramp control, making it possible to ramp
different groups at different rates. The ramp-up and
ramp-down times are controlled by the LED__RU and
LED__RD control bits, and the ramps are enabled/dis-
abled by the LED__RAMP_EN bits. The ICs increase or
decrease the current one step every t RAMP /32 until the
target LED current is reached.
Open/Short Detection
The ICs include comparators to detect open or shorted
LEDs on LED1 and LED2. One comparator on each LED_
output detects when the voltage falls below 100mV, indi-
cating an open LED fault. Another comparator on each
LED_ output detects when the voltage rises above V OUT2
- 1V, indicating a shorted LED fault. The fault-detection
comparators are enabled only when the corresponding
LED_ current regulator is enabled and provides a con-
tinuous monitor of the current regulator conditions.
Once a fault is detected, it is flagged in the EVENT_B
register and the IRQ signal is asserted (unless masked
in the IRQ_MASK_B register).
Overvoltage Protection
If the voltage on the OUT2 rises above 28V (typ), the
LED driver is put into the shutdown state. This protects
the ICs from excessive voltage in the event of an open-
circuit LED.
Vibrator Driver
The vibrator driver is an LDO with PWM control (see
Figure 8). The LDO output voltage is programmable
through I 2 C to 1.3V, 2.5V, 3.0V, and V BATT .
The vibrator driver is driven with a PWM signal of duty
cycle from 0% to 83% or 100%, with a repetition fre-
quency of 23.8kHz divided into 84 steps. A PWM ratio
set to greater than 83 results in the vibrator output being
permanently enabled (100%). Figure 9 shows the output
waveform at different output voltage and PWM settings.
The duty cycle is set by the I 2 C interface, with a value
greater than 0 enabling the PWM mode of operation. By
using the enable/disable, an active stop is activated.
CHARGER DETECTED
UVLO COMPARATOR
DELAY
OUTVIB
VIB DRIVER
INVIB
BATT
DEBOUNCE 250ms ±40%
CHARGER PROCESS
OVP INTERRUPT
M
PWM
I 2 C
Figure 7. Timing of OVP Detection
24
Figure 8. Vibrator Driver
Maxim Integrated
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| MAX8939QEWV+T | 制造商:Maxim Integrated Products 功能描述:SYSTEM POWER - Tape and Reel |
| MAX893LESA | 功能描述:电源开关 IC - USB 1.2A Current-Limited High-Side PCh Switch RoHS:否 制造商:Micrel 电源电压-最小:2.7 V 电源电压-最大:5.5 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:SOIC-8 封装:Tube |
| MAX893LESA+ | 功能描述:电源开关 IC - USB 1.2A Current-Limited High-Side PCh Switch RoHS:否 制造商:Micrel 电源电压-最小:2.7 V 电源电压-最大:5.5 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:SOIC-8 封装:Tube |
| MAX893LESA+T | 功能描述:电源开关 IC - USB 1.2A Current-Limited High-Side PCh Switch RoHS:否 制造商:Micrel 电源电压-最小:2.7 V 电源电压-最大:5.5 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:SOIC-8 封装:Tube |
| MAX893LESA-T | 功能描述:电源开关 IC - USB 1.2A Current-Limited High-Side PCh Switch RoHS:否 制造商:Micrel 电源电压-最小:2.7 V 电源电压-最大:5.5 V 最大工作温度:+ 85 C 最小工作温度:- 40 C 封装 / 箱体:SOIC-8 封装:Tube |
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