Features

VIN range: 3.0V to 5.5V

dual independent current limit

-75 mia to 1200 mia

-± 10%current accuracy

-20 ° C temperature zone

reverse current atresia protection

power supply Delive

Low static current

-The typical value 40 μA

-Dims of maximum 1.0 μA

65MΩ Typical RDS ( Open), 3V

Enable control pin only requires 1.4V

Obscaner lock

Temperature range: -40 to 85 ° C

12-shot TSOPJW packaging or 14-pin TDFN33 packaging

Application

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Capacitor charger

CF card port power supply

fast card GSM/GPRS/3G modem

] PC card GSM/GPRS level 10/12 modem

wIMAX card

General description

aat4621

Smartswitch is A current PChannel MOSFET power switch is designed for high -end load switching applications in the PC card GSM/GPRS/3G modem card. When used with supercapacitors, AAT4621 will ensure that the rated power of the PCMCIA host will not exceed any time. The programmable capacitor T4621 can be charged independently without two current restrictions. The current limit is set by two external resistors, allowing ± 10%of the current limit accuracy within the normal operating temperature range. The switch can be controlled by any of the input in the input. When disconnect, the current in the two directions will be blocked. AAT4621 also contains a systematic funny function, which can notify the system supercapacitors that have been fully charged and prepared. The adjustable stagnation is achieved by adding an external resistor. Static power currents are often 40 μA. In the shutdown mode, the power supply current is reduced to less than 1 μA.

AAT4621 provides a thermal enhancement type, lead, 12-pin TSOPJW or 14-pin TDFN33 packaging, the temperature range is40 ° C to 85 ° C.

Typical application

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Function box diagram

Function description

AAT4621 is an integrated P channel MOSFET load switch, which has an independent enabled upper topic The lower limit can adjust the current, over -temperature protection, power circuit and supercapacitors charger. The combination of current limit control with ultra -temperature heat limit and power circuit circuit provides a comprehensive system to protect the load switch and its power supply from being affected by load conditions exceeding the power specifications. AAT4621 is specifically designed to provide interfaces between PCMCIA hosts and PC cards. Using a super capacitor average high pulse current on the PCMCIA host and PC card, otherwise it will exceed the PCMCIA/Express card power specifications. E, G.GSM/GPRS modem card card, the pulse current can exceed 1A maximum specifications during the transmission signal (for Express card, 1.3A).

Independent work of current and ultra -temperature circuit. When the output load current exceeds the internal threshold level, the equipment current limit is activated. There are two independent internal current restrictions. The current limit threshold in each case is determined by the external resistor connected between the two settings pins and ground. The minimum current limit threshold is specified by ILIM (min). If the load conditions keep the device at the current limit and the chip temperature reaches the critical point, the internal power circuit will reduce the current to the safe level. Connecting the Isetu to the ground will be disabled and protected by the disabled current, and the low impedance path is allowed to connect to the host VCC.

Two high levels of the two EN pins of the load switch through the application logic. When the two exist at the same time, the EN-IU will choose ISETU. The EN function has a logical flat threshold, allowing AAT4621 to be compatible with TTL, or it can also be controlled from 2.5V to 5.0V CMOS circuits. The voltage level applied on the EN pin should not exceed the input power level on the VCC pin. Generally, when the current output from T4 1 is blocked, the current output from T4 1 decreases.

The locking circuit of the IOU ensures that the VCC power supply is high enough to work normally. It also includes a systematic fun. When the capacitor voltage is charged and the load is allowed to accept the current, the function will be activated. For automatic function, this pin can be directly connected to the EN-IU pin. A external resistor is provided to increase the lag of the function.

Application information

Isetu and ISETL current limit settings

AAT4621 current limit settings to two different levels. Isetl and ISETThe resistors of U set the lower limit and upper limit of the current.

Isetl and ISETU nodes work in windows from 0.75V to 1.5V, with the resistance value between 93.75Ω and 1.5MΩ. It is not recommended to exceed this range. Isetl and Isetu source current change with the resistance value used in Table 1. To determine the current limit, multiply the voltage of the RSetu or RSetl node as the gain in Table 1. Note that the voltage at the node changes between 0.75V and 1.5V, and the current limit gain changes according to the resistance value used.

If the setting pin is opened or allowed to exceed 2V, all the power supply equipment will be disabled and the input and output are disconnected. Put the SET pin to GND to enable all the power supply equipment, and the VCC is short -circuited with the output pin, and there is no current restriction.

To activate the current level (RSETU), lower EN IU. To activate low current (RSETL), lower EN IL. If EN-IU and EN-IL are pulled down, you will select the EN-IU current limit level (RSETU).

Systems with stagnation (RHYS) and Systems Ready (RDY)

Internal comparator detect the output voltage, when the output voltage reaches the final value ( At 98%of VCC, send a ready signal to the external microcontroller. The comparison delay from RHYS to the ground resistance programming. The RHYS voltage determines the lag voltage, which is equal to the RHYS source current (1 μA) by RHYS resistance.

The system is ready (RDY) is an open leak output. When the output voltage reaches 98%of the input voltage, it will switch to the low level. It requires an external pull -up resistor that is connected to the input voltage with a typical value of 100kΩ.

Power loop

AAT4621 Power Ring circuit Limit the load current when the equipment consumes too much power consumption. The AAT4621 power circuit adjusts the mold temperature to 110 ° C. When the mold temperature reaches 110 ° C, the current limit setting value is 1/32 to increase the load current. When the mold temperature exceeds 110 ° C, it reduces the load current to 1/32 of the setting value of the current limit. If the mold temperature is lower than 110 ° C, the load current is increased by 1/32 of the current limit setting value, until the setting current limit point or mold temperature exceeds 110 ° C.

The delay time between the temperature measurement of the mold depends on the setting value of the load current limit. For 75mA current limit settings, the delay range is 0.5ms; for the 1.2A current limit setting value, the delay range is 4ms.

For the situation without current limit settings (RSETU orRSETL is short -circuited on the ground), and the soft startup increases the current limit of 1.2A, until the current reaches 1.2A, at this time the power MOSFET is completely opened. At this time, the current is limited by the RDS (ON) and other series resistance of the power MOSFET. The power circuit and overheating circuit are then controlled until the output voltage is completely charged.

Overheating protection

If the temperature of the mold rises fast enough, exceeding the temperature specified by the power circuit, the over -temperature shutdown opportunity will fail the equipment. The ultra -temperature threshold is 145 ° C. After the ultra -temperature stop, once the mold temperature drops to 130 ° C, the soft start is started.

Short -circuit protection

When the output end is charged within 18mV of the input voltage, the series power MOSFET will be completely closed. In the case of short -circuited output, this can protect the equipment. After the output is applied to a short -circuit or heavy load, the output drops to the 18MV threshold and add some lags below the threshold. The current will immediately try to convert from zero to the final programming value. As long as the output is Vin 18mV or until the mold temperature reaches 110OC, the device will continue to output current limit. If the temperature returns, the power circuit will activate.

Impurd pressure stop

The owed voltage locking makes the device work normally under 2.7V voltage, lagging behind 100mV. The maximum UVLO level is 3.0V.

Digital programming soft startup current limit

When the opening of the digital soft start is equivalent to the discrete range of the final programming current limit setting value of 1/32, the load current increases from zero to final programming current Restricted levels.

Once AAT4621 is fully charged with supercapacitors, the soft -raising circuit will be disabled. The soft -starting function is re -activated only in the following circumstances:

1. The power supply or enable cycle to turn off and reopen.

2. Start at the heat shutdown

3. Switch from ENU to ENL, vice versa, or

4. After the current event, such as hard output short circuit.

Reverse current atresia

When the input voltage is less than the output voltage, the internal comparator will disable the intimable transistor to block any reverse current from the output to the input. Evaluation Committee The evaluation board schematic diagram is shown in Figure 2. The PCB layout encapsulated by TSOP is shown in Figure 3 and 4. The layout of the TDFN package is shown in Figure 5 and Figure 6.

Packaging information

1. Millimeter.

2. xyy u003d assembly and date code.

3. Sample inventory is usually based on the part number displayed by the thick body.123]

4. Lead -free packaging series include QFN, TQFN, DFN, TDFN, and STDFN. Due to the manufacturing process, there are naked copper (unsolved) at the end of the lead terminal.The welding angle of the exposed copper edge cannot be guaranteed, nor does it need to ensure that the bottom welding connection is correct.

1. All units are millimeters.