Advanced AMS2027 Monolithic SINGLE POWER DISTRIBUTION SWITCH Systems
PRELIMINARY INFORMATION
FEATURES
• 110mΩ Typical (5V Input) High Side MOSFET Switch• Short Circuit Protection
• Logic Overcurrent Output Error Flag• Logic Undervoltage Output Error Flag• Logic Overheat Output Error Flag
• Enable Input Compatible With 3V and 5V Logic• Controlled Rise and Fall Times Limit Current Surges and Minimize EMI
• Undervoltage Lock-Out Guarantees the Switch is Off At Start-up
• 100µA Maximum On-State Supply Current• Available Active-High or Active-Low Enable
• Available in Space Saving 8 lead SOIC and 8 Lead PDIP
APPLICATIONS
• USB Power Management• Hot Plug-In Power Supplies• Battery-Charger Circuits
PRODUCT DESCRIPTION
The AMS2027 is a power distribution switch intended for application where heavy capacitive loads and short-circuits arelikely to be encountered. The high-side switch is a 110mΩ N-channel MOSFET. The switch is controlled by a logic enableinput compatible with 3V and 5V logic and is available in active-high or active-low enable. The internal charge pump,designed to control the power switch rise and fall time to minimize current surges during switching, also provides the gatedrive. Requiring no external components the charge pump allows operation from supplies as low as 3.3V. When an overloador a short circuit is encountered the AMS2027 limits the output current to a safe level by switching into a constant-currentmode and the overcurrent logic output error flag is set to a low. The power dissipation in the switch will be increased bycontinuous heavy overloads and short circuits; this will cause the junction temperature to rise. The thermal protection circuitshuts the power switch off to prevent damage. Once the device has cooled sufficiently, it will turn on automatic. An undervoltage lock-out is provided to insure that the power switch is in the Off state at start-up.
The AMS2027 is offered in the 8 lead SOIC package and the 8 lead PDIP package and is rated operational over a -40°C to85°C temperature range.
ORDERING INFORMATION
PACKAGE TYPE
8 LEAD SOICAMS2027S
8 LEAD PDIPAMS2027P
OPER. TEMPRANGE-40°C to 85°C
PIN CONNECTIONS
8 LEAD SOIC/ 8LEAD PDIPENABLEERRORGROUNDN/C12348OUTPUT7INPUT6OUTPUT5N/CAdvanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
元器件交易网www.cecb2b.com
AMS2027
ABSOLUTE MAXIMUM RATINGS (Note 1)
Input Voltage Range, VIOutput Voltage Range, VO
Input Voltage Range, VI at /ENContinuos Output Current, IO
-0.3V to 7V
-0.3V to VI(IN) +0.3V
-0.3V to 7V
Internal Power Dissipation (Note 3)Maximum Junction TemperatureStorage Temperature
Lead Temperature (Soldering 10 sec)
Internally Limited
+125°C
-65°C to +150°C
260°C
ELECTRICAL CHARACTERISTICS
Electrical Characteristics at TJ=25°C, VI(IN) = 5.5V, IO =rated current, /EN = 0V unless otherwise specified.
PARAMETER
Switch On-State Resistance
VI(IN) = 5.5VVI(IN) = 5.0VVI(IN) = 4.5VVI(IN) = 4.0V
Switch Output Leakage Current
/EN = VI
/EN = VI , -40°C ≤ TJ ≤ 85°C
Switch Output Rise Time
VI(IN) = 5.5V, CL = 1µFVI(IN) = 2.7V, CL = 1µF
Switch Output Fall Time
VI(IN) = 5.5V, CL = 1µFVI(IN) = 2.7V, CL = 1µF
Enable High-Level Input VoltageEnable Low-Level Input VoltageEnable Input Current
Enable Delay Time, Low-to-HighOutput
Short Circuit Current
4.0V ≤ VI ≤ 5.5V4.0V ≤ VI ≤ 5.5V/EN = 0V or /EN = VICL = 1µFCL = 1µF
VI(IN) = 5.5V, TJ=25°C
OUT Connected to GND, device enable intoshort circuit
Supply Current, Low-LevelOutput
Supply Current, High-LevelOutput
/EN = VI , TJ=25°C/EN = VI , -40°C ≤ TJ ≤ 85°C/EN = 0V, TJ=25°C/EN = 0V, -40°C ≤ TJ ≤ 85°C
730.015
1010100100
µAµAµAµA0.66
1.2
-1.02.4
.061.020401.8
4.03.83.93.5
CONDITIONS
(Note 2)
Min.
AMS2027Typ.
758090960.01
Max.
9595110110510
Units
mΩmΩmΩmΩµAµAmsmsmsmsVVµAmsmsA
Undervoltage lock-out Low-Level2.03.03.2VInput Voltage
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. For guaranteed performance limits and associated test conditions, seethe Electrical Characteristics tables.
Note 2: To ensure constant junction temperature, low duty cycle pulse testing is used; thermal effects must be taken in consideration separately.
Note 3: The Power Dissipation for the SO-8 package is 725mW at TA = 25 °C. Above TA = 25 °C the Power Dissipation must be derated at 5.8mW/ °C (for TA =70 °C PD = 464mW ; for TA = 125 °C PD = 145mW)
RECOMENDED OPERATING CONDITIONS:Input Voltage, VI
Input Voltage, VI at /EN
Continuous Output Current, IOOperating Junction Temp. Range
Min4.0V0V0A-40°C
Max5.5V5.5V0.6A+125°C
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
元器件交易网www.cecb2b.com
AMS2027
PIN FUNCTIONS
Pin Name
Enable/ENGroundGNDInputINError FlagERROROutputOUT
Pin No.
13726,8
I / OIIIOO
Description
Enable Input, Logic turns power switch on.Ground.
Power switch input, also supplies IC’s internal circuitry.Overcurrent, Over temperature, Logic output.Power switch output.
BLOCK DIAGRAM
OUT
*CSPOWER SWITCHIN1.2VREFERENCECURRENTLIMITENABLEERRORFLAGCHARGEPUMPGATEDRIVERTHERMALSENSEUVLOERRORGND
*Current Sense
FUNCTIONAL DESCRIPTION
Power Switch
The power switch is an N-channel MOSFET with a maximum on-state resistance of 140mΩ (VI(IN) = 5.0V, configured as a high-side switch.Charge Pump
An internal 100kHz charge pump supplies the power to the drivercircuit and provides the required voltage to pull the gate of theMOSFET above the source. The charge pump requires very littlesupply current and operates from input voltages as low as 3.3V.Gate Driver
The driver controls the gate voltage of the power switch. Thedriver incorporates circuitry that controls the rise and fall times ofthe output voltage, as a result it limits large current surges andreduces the associated electromagnetic interference (EMI)produced. The rise and fall times of the output voltage aretypically in the 2ms to 4ms range instead of the microsecond ornanosecond range for a standard FET.Enable
A logic high on the /EN input turns off the power switch and thebias for the charge pump, driver, and other circuitry to reduce thesupply current to less than 10µA. A logic zero input restore biasto the drive and control circuits and turns the power on. Theenable input is compatible with both TTL and CMOS logiclevels.
Error Flag
The error flag output, is an open drain logic output that is activelow when output current exceeds current limit. Until the faultcondition is removed the output will remain active low.Current Limit
A sense FET monitors the current supplied to the load. In case ofan overload or short circuit, the current limit circuitry sends asignal to the driver. The driver will then reduce the gate voltageand drive the power FET into its linear region, which switchesthe output into a constant current mode and holds the currentconstant while varying the voltage on the load.Thermal Shutdown
The internal thermal shutdown circuit will shut the power switchoff when the junction temperature rises to approx. 180°C.Hysterisis is build into the thermal sense circuitry, and after thejunction temperature has dropped about 20°C, the switch turnsback on. Until the fault is removed the switch will continue tocycle off and on.
Undervoltage Lock-out
An internal voltage sense monitors the input voltage. When theinput voltage is below 3.2V nominal, the switch is turned off by acontrol signal. The typical fall time range due to the sense of alow voltage is 250µs to 750µs.
Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
元器件交易网www.cecb2b.com
AMS2027
APPLICATION HINTS
Power Supply Considerations
A 0.047µF ceramic bypass capacitor close to the device, betweeninput and ground is recommended. When the output load is heavyor has large paralleled capacitors, a high value electrolyticcapacitor should be used. To improve the immunity of the deviceto ESD, use a 0.1µF ceramic capacitor to bypass the output.Current Limit
A sense FET monitors overcurrent conditions. When anovercurrent condition is detected the device maintains a constantoutput current and decreases the voltage accordingly. If thecondition is present long enough to activate the thermal limitingthe result is the shutdown of the device.
There are three situation in which overload can occur. In the firstcase, the output has been shorted before the device is enabled orbefore VI has been applied. The device senses the short andswitches into a constant-current output.
In the second case, the short occurs while the device is enabled.When this happens, very high currents flow for a short timebefore the current-limit circuit can react. After the current-limitcircuit has tripped, the device limits normally.
In the third case, the load has been gradually increased beyondthe recommended operating current. The current will rise untilthe current-limit threshold is reached. The AMS2027 is able todeliver current up to the current-limit threshold without damage.When the threshold has been reached the device switches into theconstant current mode. When over current condition is detectedthe error flag logic output remains low until the condition isremoved.
Power Dissipation and Junction Temperature
The thermal resistance of the surface-mount packages such asSOIC is high compared to that of power packages. The use of theN-cannel MOSFET which has low on-resistance, makes itpossible for small surface-mount packages to pass large currents.To determine the power dissipation and junction temperature thefirst step is to find rON at the input voltage and operatingtemperature.
As an initial estimate use the highest operating ambienttemperature of interest and read rON from Figure1. Powerdissipation is equal to: PD = rON X I2
Calculate the junction temperature: TJ = PD X RθJA + TA
Where RθJA is the thermal resistance and is 172°C/W for theSOIC package. Compare the calculated junction temperature withthe initial estimate and if they don’t mach within a few degrees,repeat the calculations using the calculated value as the newestimate. A few repetitions will be sufficient to give a reasonableanswer.
Thermal Protection
Thermal protection prevents damage to the device when overload or short circuits conditions are present for extended periodsof time. These conditions force the AMS2027 into the constantcurrent mode. As a result the voltage across the high-side switchwill increase. Under short-circuit conditions the voltage acrossthe switch is equal to the input voltage. Continuous heavy overloads and short circuits increase the power dissipation in theswitch and causes the junction temperature to rise to dangerouslyhigh levels. The protection circuit shuts off the switch when itsenses the high junction temperature. The switch remains offuntil the device has cooled about 20°C. The switch continues tocycle off and on until the fault is removed.Undervoltage Lock-out
An undervoltage lock-out is provided to insure that the switch isin the off state at start-up. When the input voltage falls below3.2V the switch will be turned off immediately. This will make iteasy for designers of hot plug-in systems that may not be able toturn the switch off before removing the input power. In suchcases when the device is reinserted, the turn on will have acontrolled rise time to reduce EMI and voltage overshoots.
TYPICAL APPLICATIONS
Figure 1
POWER SUPPLY
4.0V - 5.0V
1µF10k0.1µF7INOUT80.1µFEXTERNAL LOAD ENABLEERROR FLAG12ENERRORGND3OUT6Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
元器件交易网www.cecb2b.com
AMS2027
PACKAGE DIMENSIONS inches (millimeters) unless otherwise noted.
8 LEAD SOIC PLASTIC PACKAGE (S)
0.189-0.197*(4.801-5.004)87651234*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASHSHALL NOT EXCEED 0.006\" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEADFLASH SHALL NOT EXCEED 0.010\" (0.254mm) PER SIDE
8 LEAD PLASTIC DIP PACKAGE (P)
0.255±0.015*(6.477±0.381)0.045-0.065(1.143-1.651)Advanced Monolithic Systems, Inc. 6680B Sierra Lane, Dublin, CA 94568 Phone (925) 556-9090 Fax (925) 556-9140
因篇幅问题不能全部显示，请点此查看更多更全内容