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| AAT4250 Slew Rate Controlled Load Switch General Description The AAT4250 SmartSwitchTM is a member of AATI's Application Specific Power MOSFETTM (ASPMTM) product family. It is a Slew Rate Controlled P-channel MOSFET power switch designed for high-side load-switching applications. This switch operates with an input voltage range from 1.8V to 5.5V, making it ideal for 2.5V, 3.3V or 5V systems. The part features 1.5ms turn on and 10s turn off time. The AAT4250 has an under voltage lock out which turns off the switch when an under-voltage condition exists. Input logic levels are TTL compatible. The quiescent supply current is very low, typically 2A. In shutdown mode, the supply current is typically reduced to 0.1A or less. The AAT4250 is available in a 5-pin SOT23 and 8pin SC70JW specified over -40 to 85C. Features * * * SmartSwitchTM * * * * 1.8V to 5.5V Input voltage range 120m (5V) typical RDS(ON) Low quiescent current * Typical 2A * Typical 0.1A with Enable off Only 2.0V needed for ON/OFF Control Temperature range -40 to 85C 5kV ESD rating 5-pin SOT23 or SC70JW-8 package Preliminary Information Applications * * * Hot swap supplies Notebook computers Personal communication devices Typical Application INPUT IN OUT OUTPUT AAT4250 SOT23 CIN 1F ON ON/OFF GND COUT 0.1F GND GND 4250.2001.12.0.94 1 AAT4250 Slew Rate Controlled Load Switch Pin Descriptions Pin # SOT23-5 1 2 3 4 5 SC70JW 1 2, 3, 4, 5 n/a 6 7, 8 Symbol OUT GND NC ON/OFF IN Function P-channel MOSFET drain Ground connection Not internally connected Active-High Enable Input (Logic high turns the switch on) P-channel MOSFET source Pin Configuration SOT23-5 (Top View) OUT GND NC 1 2 3 5 IN 4 ON/OFF SC70JW-8 (Top View) OUT GND GND GND 1 2 8 7 3 4 6 5 IN IN ON/OFF GND 1 2 2 4250.2001.12.0.94 AAT4250 Slew Rate Controlled Load Switch Absolute Maximum Ratings Symbol VIN VON VOUT IMAX IDM TJ TLEAD VESD (TA=25C unless otherwise noted) Value -0.3 to 6 -0.3 to 6 -0.3 to VIN+0.3 1.7 4 2 -40 to 150 300 5000 Description IN to GND ON/OFF to GND OUT to GND Maximum Continuous Switch Current Maximum Pulsed Current Operating Junction Temperature Range Maximum Soldering Temperature (at Leads) ESD Rating1 - HBM IN 2.5V IN < 2.5V Units V V V A A A C C V Note: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum rating should be applied at any one time. Note 1: Human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin. Thermal Characteristics Symbol JA PD Description Thermal Resistance (SOT23-5 or SC70JW-8) Power Dissipation (SOT23-5 or SC70JW-8)2 2 Value 150 667 Units C/W mW Note 2: Mounted on an AAT4250 demo board in still 25C air. Electrical Characteristics are at TA=25C) Symbol VIN IQ IQ(OFF) ISD(OFF) VUVLO VUVLO(hys) RDS(ON) TCRDS VIL VIH ISINK TD TOFF TOFF TON TON TON (VIN = 5V, TA = -40 to 85C unless otherwise noted. Typical values Conditions VIN = 5V, ON/OFF = VIN, IOUT = 0 ON/OFF = GND, VIN = 5V, OUT open ON/OFF = GND, VIN = 5V, VOUT = 0 VIN falling VIN = 5V VIN = 3V VIN =1.8V VIN = 2.7V to 5.5V3 VIN = 2.7V to 4.2V VIN = > 4.2V to 5.5V VON = 5V VIN=5V, RLOAD=10 VIN=3V, RLOAD=5 VIN=5V, RLOAD=16.5 , TA=0 to 50 C VIN=5V, RLOAD=10 , COUT=0.1F VIN=3V, RLOAD=5 , COUT=0.1F Description Operation Voltage Quiescent Current Off Supply Current Off Switch Current Undervoltage Lockout Undervoltage Lockout hysteresis On-Resistance On-Resistance Temp-Co ON/OFF Input Logic Low Voltage ON/OFF Input Logic High Voltage ON Input leakage Output Turn-On Delay Time Turn-Off Fall Time Turn-Off Fall Time Turn-On Rise Time Turn-On Rise Time Turn-On Rise Time Min 1.8 Typ 2 0.1 1.5 250 120 135 165 2800 Max 5.5 4 1 1 Units V A A A V mV m m m ppm/C V V 175 200 0.8 2.0 2.4 0.01 300 1 10 10 1000 1500 1500 A s s s s s s Note 3: For VIN outside this range consult typical ON/OFF threshold curve. 4250.2001.12.0.94 3 AAT4250 Slew Rate Controlled Load Switch Typical Characteristics (Unless otherwise noted, VIN = 5V, TA = 25C) Quiescent Current vs. Temperature 4 4 Quiescent Current vs. VIN Quiescent Current (A) Quiescent Current (A) 3.5 3 2.5 2 1.5 1 0.5 0 -40 -20 0 20 40 60 80 100 3.5 3 2.5 2 1.5 1 0.5 0 0 1 2 3 4 5 6 VIN=5V VIN=3V Temperature (C) VIN Off-Supply Current vs. Temperature 1000 Off-Switch Current vs. Temperature 10000 Off-Supply Current (nA) Off-Switch Current (nA) -20 0 20 40 60 80 100 1000 100 100 10 10 1 -40 1 -40 -20 0 20 40 60 80 100 Temperature (C) Temperature (C) Turn-OFF Time vs. Temperature CIN=1F, COUT=0.1F 10 3.0 Turn-On Time vs. Temperature CIN=1F, COUT=0.1F Turn-OFF Time (s) Turn-ON Time (ms) 9 8 7 6 5 -40 2.5 2.0 1.5 1.0 0.5 -40 VIN=5V RLOAD=10 VIN=3V RLOAD=5 VIN=5V RLOAD=10 VIN=3V RLOAD=5 -20 0 20 40 60 80 100 -20 0 20 40 60 80 100 Temperature (C) Temperature (C) 4 4250.2001.12.0.94 AAT4250 Slew Rate Controlled Load Switch (Unless otherwise noted, VIN = 5V, TA = 25C) Turn On Waveforms CIN=1F,COUT=0.1F,VIN=3V 4 2 6 5 1.5 1 Turn On Waveforms CIN =1F,COUT =0.1F,VIN =5V 1.2 V(ON/OFF) 3 V(ON/OFF) V(out) 1 0.8 0.6 0.4 Volt 2 A 3 2 1 0.5 I(in) 1 0.2 0 -1 0 1 2 3 4 0 I(in) 0 -1 0 1 2 3 4 0 Time (ms) Time (ms) Turn On Waveforms CIN =1F,COUT =10F,VIN =3V 4 2 6 5 1.5 Turn On Waveforms CIN =1F,COUT =10F,VIN =5V 1.2 V(ON/OFF) 3 V(ON/OFF) V(out) 1 0.8 Volt Volt V(out) 4 A 2 1 0.5 I(in) 0.4 0.2 0 I(in) 0 -1 0 1 2 3 4 0 1 0 -1 0 1 2 3 4 Time (ms) Time (ms) Turn Off Waveforms CIN =1F,COUT =1F,VIN =3V 4 5 3 Turn Off Waveforms CIN =1F,COUT =1F,VIN =5V V(out) V(out) Volt 1 Volt 2 3 V(ON/OFF) 0 -1 -1 1 3 5 7 9 11 13 15 1 V(ON/OFF) 1 3 5 7 9 11 13 15 -1 -1 Time (s) Time (s) 4250.2001.12.0.94 A 2 1 3 0.6 A V(out) Volt 4 5 AAT4250 Slew Rate Controlled Load Switch (Unless otherwise noted, VIN = 5V, TA = 25C) RDS(ON) vs. Temperature 160 190 180 RDS(ON) vs. VIN RDS(ON) (m) RDS(ON) (m) 170 160 150 140 130 120 IOUT = 100mA VIN=3V 120 VIN=5V 80 -40 -20 0 20 40 60 80 100 110 1.5 2 2.5 3 3.5 4 4.5 5 5.5 Temperature (C) VIN Typical ON/OFF Threshold vs. VIN 2.2 ON/OFF Threshold 2.0 1.8 1.6 1.4 1.2 1.0 0.8 0.6 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 VIH VIL V IN 6 4250.2001.12.0.94 AAT4250 Slew Rate Controlled Load Switch Functional Block Diagram IN Slew Rate Control OUT Undervoltage Lockout Level Shift ON/OFF GND Functional Description The AAT4250 is a slew rate controlled P-channel MOSFET power switch designed for high-side loadswitching applications. It operates with input voltages ranging from 1.8V to 5.5V which, along with its extremely low operating current, makes it ideal for battery-powered applications. In cases where the input voltage drops below 1.8V, the AAT4250 MOSFET is protected from entering the saturated region of operation by automatically shutting down. In addition, the TTL compatible ON/OFF pin makes the AAT4250 an ideal level shifted load-switch. The slew rate controlling feature eliminates in-rush cur- rent when the MOSFET is turned on, allowing the AAT4250 to be implemented with a small input capacitor, or no input capacitor at all. During slewing, the current ramps linearly until it reaches the level required for the output load condition. The proprietary control method works by careful control and monitoring of the MOSFET gate voltage. When the device is switched ON, the gate voltage is quickly increased to the threshold level of the MOSFET. Once at this level, the current begins to slew as the gate voltage is slowly increased until the MOSFET becomes fully enhanced. Once it has reached this point, the gate is quickly increased to the full input voltage and RDS(ON) is minimized. 4250.2001.12.0.94 7 AAT4250 Slew Rate Controlled Load Switch Applications Information Input Capacitor Typically a 1F or larger capacitor is recommended for CIN in most applications. A CIN capacitor is not required for basic operation, however, it is useful in preventing load transients from affecting up stream circuits. CIN should be located as close to the device VIN pin as practically possible. Ceramic, tantalum or aluminum electrolytic capacitors may be selected for CIN. There is no specific capacitor ESR requirement for CIN. However, for higher current operation, ceramic capacitors are recommended for CIN due to their inherent capability over tantalum capacitors to withstand input current surges from low impedance sources such as batteries in portable devices. In applications where there is a possibility of VOUT exceeding VIN for brief periods of time during normal operation, the use of a larger value CIN capacitor is highly recommended. A larger value of CIN with respect to COUT will effect a slower CIN decay rate during shutdown, thus preventing VOUT from exceeding VIN. In applications where there is a greater danger of VOUT exceeding VIN for extended periods of time, it is recommended to place a schottky diode from VIN to VOUT (connecting the cathode to VIN and anode to VOUT). The Schottky diode forward voltage should be less then 0.45 volts. Thermal Considerations and High Output Current Applications The AAT4250 is designed to deliver a continuous output load current. The limiting characteristic for maximum safe operating output load current is package power dissipation. In order to obtain high operating currents, careful device layout and circuit operating conditions need to be taken into account. The following discussions will assume the load switch is mounted on a printed circuit board utilizing the minimum recommended footprint as stated in the layout considerations section. At any given ambient temperature (TA) the maximum package power dissipation can be determined by the following equation: PD(MAX) = [TJ(MAX) - TA] / JA Constants for the AAT4250 are maximum junction temperature, TJ(MAX) = 125C, and package thermal resistance, JA = 150C/W. Worst case conditions are calculated at the maximum operating temperature where TA = 85C. Typical conditions are calculated under normal ambient conditions where TA = 25C. At TA = 85C, PD(MAX) = 267mW. At TA = 25C, PD(MAX) = 667mW. The maximum continuous output current for the AAT4250 is a function of the package power dissipation and the RDS of the MOSFET at TJ(MAX). The maximum RDS of the MOSFET at TJ(MAX) is calculated by increasing the maximum room temperature RDS by the RDS temperature coefficient. The temperature coefficient (TC) is 2800ppm/C. Therefore, at 125C RDS(MAX) = RDS(25C) x (1 + TC x T) RDS(MAX) = 175m x (1 + .002800 x (125C - 25C)) RDS(MAX) = 224m 4250.2001.12.0.94 Output Capacitor For proper slew operation, a 0.1F capacitor or greater between VOUT and GND is required. Likewise, with the output capacitor, there is no specific capacitor ESR requirement. If desired, COUT maybe increased without limit to accommodate any load transient condition without adversely affecting the slew rate. Enable Function The AAT4250 features an enable / disable function. This pin (ON) is active high and is compatible with TTL or CMOS logic. To assure the load switch will turn on, the ON control level must be greater than 2.0 volts. The load switch will go into shutdown mode when the voltage on the ON pin falls below 0.8 volts. When the load switch is in shutdown mode, the OUT pin is tristated, and quiescent current drops to leakage levels below 1A. Reverse Output to Input Voltage Conditions and Protection Under normal operating conditions a parasitic diode exists between the output and input of the load switch. The input voltage should always remain greater than the output load voltage maintaining a reverse bias on the internal parasitic diode. Conditions where VOUT might exceed VIN should be avoided since this would forward bias the internal parasitic diode and allow excessive current flow into the VOUT pin and possibly damage the load switch. 8 AAT4250 Slew Rate Controlled Load Switch For maximum current, refer to the following equation: IOUT(MAX) < ( PD(MAX) / RDS)1/2 For example, if VIN = 5V, RDS(MAX)=224m and TA = 25C, IOUT(MAX) = 1.7A. If the output load current were to exceed 1.7A or if the ambient temperature were to increase, the internal die temperature will increase, and the device will be damaged. Higher peak currents can be obtained with the AAT4250. To accomplish this, the device thermal resistance must be reduced by increasing the heat sink area or by operating the load switch in a duty cycle manner. Duty cycles with peaks less than 2ms in duration can be considered using the method below. by consulting the chart of RDSON vs. VIN. The Rds reported for 5 volt RDS can be scaled by the ratio seen in the chart to derive the Rds for 4 volt VIN: 175m x 120m/115m = 183m. Derated for temperature: 183m x (1 + .002800 x (125C 25C)) = 235m . The power dissipation for a 100mA load is calculated as follows: PD(MAX) = I2OUT x RDS PD(100mA) = (100mA)2 x 235m PD(100mA) = 2.35mW PD(87.5%D/C) = %DC x PD(100mA) PD(87.5%D/C) = 0.875 x 2.35mW PD(87.5%D/C) = 2.1mW The power dissipation for 100mA load at 87.5% duty cycle is 2.1mW. Now the power dissipation for the remaining 12.5% of the duty cycle at 2A is calculated: PD(MAX) = I2OUT x RDS PD(2A) = (2A)2 x 235m PD(2A) = 940mW PD(12.5%D/C) = %DC x PD(2A) PD(12.5%D/C) = 0.125 x 940mW PD(12.5%D/C) = 117.5mW The power dissipation for 2A load at 12.5% duty cycle is 117mW. Finally, the two power figures are summed to determine the total true power dissipation under the varied load. PD(total) = PD(100mA) + PD(2A) PD(total) = 2.1mW + 117.5mW PD(total) = 120mW The maximum power dissipation for the AAT4250 operating at an ambient temperature of 85C is 267mW. The device in this example will have a total power dissipation of 120mW. This is well with in the thermal limits for safe operation of the device, in fact, at 85C, the AAT4250 will handle a 2A pulse for up to 28% duty cycle. At lower ambient temperatures the duty cycle can be further increased. High Peak Output Current Applications Some applications require the load switch to operate at a continuous nominal current level with short duration high current peaks. Refer to the IDM specification in the Absolute Maximum table to ensure the AAT 4250's maximum pulsed current rating is not exceeded. The duty cycle for both output current levels must be taken into account. To do so, first calculate the power dissipation at the nominal continuous current level, and then add in the additional power dissipation due to the short duration high current peak scaled by the duty factor. For example, a 4V system using an AAT4250 operates at a continuous 100mA load current level and has short 2A current peaks, as in a GSM application. The current peak occurs for 576s out of a 4.61ms period. First, the current duty cycle is calculated: % Peak Duty Cycle: X/100 = 576s/4.61ms % Peak Duty Cycle = 12.5% The load current is 100mA for 87.5% of the 4.61ms period and 2A for 12.5% of the period. Since the Electrical Characteristics do not report RDS MAX for 4 volts operation, it must be calculated approximated 4250.2001.12.0.94 9 AAT4250 Slew Rate Controlled Load Switch Printed Circuit Board Layout Recommendations For proper thermal management, and to take advantage of the low RDSON of the AAT4250, a few circuit board layout rules should be followed: Vin and Vout should be routed using wider than normal traces, and GND should be connected to a ground plane. For best performance, CIN and COUT should be placed close to the package pins. Evaluation Board Layout The AAT4250 evaluation layout follows the printed circuit board layout recommendations, and can be used for good applications layout. Note: Board layout shown is not to scale. Figure 1: Evaluation board top side silk screen layout / assembly drawing Figure 2: Evaluation board component side layout Figure 3: Evaluation board solder side layout 10 4250.2001.12.0.94 AAT4250 Slew Rate Controlled Load Switch Ordering Information Package SOT23-5 SC70JW-8 Marking Part Number Bulk N/A N/A Tape and Reel AAT4250IGV-T1 AAT4250IJS-T1 Package Information SOT23-5 e S1 Dim A A1 A2 b c D E e H L S S1 E H D A2 A c L Millimeters Min Max 1.00 1.30 0.00 0.10 0.70 0.90 0.35 0.50 0.10 0.25 2.70 3.10 1.40 1.80 1.90 2.60 3.00 0.37 0.45 0.55 0.85 1.05 1 9 Inches Min Max 0.039 0.051 0.000 0.004 0.028 0.035 0.014 0.020 0.004 0.010 0.106 0.122 0.055 0.071 0.075 0.102 0.118 0.015 0.018 0.022 0.033 0.041 1 9 S b 4250.2001.12.0.94 11 AAT4250 Slew Rate Controlled Load Switch SC70JW-8 e e e Dim E E1 L A A1 A2 D e b c 1 E b D 0.048REF c A2 A Millimeters Min Max 2.10 BSC 1.75 2.00 0.23 0.40 1.10 0 0.10 0.70 1.00 2.00 BSC 0.50 BSC 0.15 0.30 0.10 0.20 0 8 4 10 Inches Min Max 0.083 BSC 0.069 0.079 0.009 0.016 0.043 0.004 0.028 0.039 0.079 BSC 0.020 BSC 0.006 0.012 0.004 0.008 0 8 4 10 A1 1 L E1 Advanced Analogic Technologies, Inc. 1250 Oakmead Parkway, Suite 310, Sunnyvale, CA 94086 Phone (408) 524-9684 Fax (408) 524-9689 12 4250.2001.12.0.94 |
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