Datasheet MAX1818 (Maxim) - 7
| Manufacturer | Maxim |
| Description | 500mA, Low-Dropout Linear Regulator in SOT23 |
| Pages / Page | 9 / 7 — MAXIMUM OUTPUT CURRENT. vs. INPUT VOLTAGE. (POWER DISSIPATION LIMIT). … |
| File Format / Size | PDF / 1.5 Mb |
| Document Language | English |
MAXIMUM OUTPUT CURRENT. vs. INPUT VOLTAGE. (POWER DISSIPATION LIMIT). MAX1818. POK Output. Operating Region and Power Dissipation
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MAX1818 500mA Low-Dropout Linear Regulator in SOT23
MAXIMUM OUTPUT CURRENT
VOUT R1 = R2 - 1
vs. INPUT VOLTAGE
1.25V
(POWER DISSIPATION LIMIT)
VIN = 2.5V TO 5.5V VOUT 600 IN OUT MAXIMUM RECOMMENDED TA = +85°C OUTPUT CURRENT TA = +70°C MAX1818 fig03 CIN COUT 1µF
MAX1818
R1 3.3µF 400 ON SHDN SET OFF V 200 OUT = 1.8V VOUT = 2.5V V R OUT = 3.3V 2 MAXIMUM OUTPUT CURRENT (mA) MAXIMUM INPUT VOLTAGE POK GND 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 INPUT VOLTAGE (V) Figure 2. Adjustable Output Using External Feedback Resistors Figure 3. Power Operating Regions: Maximum Output vs. Supply Voltage
POK Output
cools by 20°C, resulting in a pulsed output during continu- The power OK (POK) output pulls low when OUT is less ous thermal overload conditions. Thermal overload protec- than 93% of the nominal regulation voltage. Once OUT tion protects the MAX1818 in the event of fault conditions. exceeds 93% of the nominal voltage, POK goes high For continuous operation, do not exceed the absolute impedance. POK is an open-drain N-channel output. To maximum junction-temperature rating of TJ = +150°C. obtain a voltage output, connect a pullup resistor from
Operating Region and Power Dissipation
POK to OUT. A 100kΩ resistor works well for most appli- cations. POK can be used as a power-okay (POK) signal The MAX1818’s maximum power dissipation depends to a microcontroller (μC), or drive an external LED to on the thermal resistance of the IC package and circuit indicate power failure. When the MAX1818 is shut down, board, the temperature difference between the die junc- POK is held low independent of the output voltage. If tion and ambient air, and the rate of air flow. The power unused, leave POK grounded or unconnected. dissipated in the device is P = IOUT × (VIN - VOUT). The maximum allowed power dissipation is 800mW at TA =
Current Limit
+70°C or: The MAX1818 monitors and controls the pass transistor’s PMAX = (TJ(MAX) - TA) / ( θJC + θCA) gate voltage, limiting the output current to 0.8A (typ). This current limit doubles when the output voltage is within 4% where TJ - TA is the temperature difference between the of the nominal value to improve performance with large MAX1818 die junction and the surrounding air, θJC is the load transients. thermal resistance of the junction to the case, and θCA is the thermal resistance from the case through the PC
Thermal Overload Protection
board, copper traces, and other materials to the surround- Thermal overload protection limits total power dissipation ing air. For best heatsinking, the copper area should be in the MAX1818. When the junction temperature exceeds equally shared between the IN, OUT, and GND pins. TJ = +170°C, a thermal sensor turns off the pass transis- The MAX1818 delivers up to 0.5A RMS and operates with tor, allowing the IC to cool. The thermal sensor turns the input voltages up to +5.5V, but not simultaneously. High pass transistor on again after the junction temperature output currents can only be sustained when inputoutput differential voltages are low, as shown in Figure 3. www.maximintegrated.com Maxim Integrated │ 7
MAXIMUM OUTPUT CURRENT
VOUT R1 = R2 - 1
vs. INPUT VOLTAGE
1.25V
(POWER DISSIPATION LIMIT)
VIN = 2.5V TO 5.5V VOUT 600 IN OUT MAXIMUM RECOMMENDED TA = +85°C OUTPUT CURRENT TA = +70°C MAX1818 fig03 CIN COUT 1µF
MAX1818
R1 3.3µF 400 ON SHDN SET OFF V 200 OUT = 1.8V VOUT = 2.5V V R OUT = 3.3V 2 MAXIMUM OUTPUT CURRENT (mA) MAXIMUM INPUT VOLTAGE POK GND 0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 INPUT VOLTAGE (V) Figure 2. Adjustable Output Using External Feedback Resistors Figure 3. Power Operating Regions: Maximum Output vs. Supply Voltage
POK Output
cools by 20°C, resulting in a pulsed output during continu- The power OK (POK) output pulls low when OUT is less ous thermal overload conditions. Thermal overload protec- than 93% of the nominal regulation voltage. Once OUT tion protects the MAX1818 in the event of fault conditions. exceeds 93% of the nominal voltage, POK goes high For continuous operation, do not exceed the absolute impedance. POK is an open-drain N-channel output. To maximum junction-temperature rating of TJ = +150°C. obtain a voltage output, connect a pullup resistor from
Operating Region and Power Dissipation
POK to OUT. A 100kΩ resistor works well for most appli- cations. POK can be used as a power-okay (POK) signal The MAX1818’s maximum power dissipation depends to a microcontroller (μC), or drive an external LED to on the thermal resistance of the IC package and circuit indicate power failure. When the MAX1818 is shut down, board, the temperature difference between the die junc- POK is held low independent of the output voltage. If tion and ambient air, and the rate of air flow. The power unused, leave POK grounded or unconnected. dissipated in the device is P = IOUT × (VIN - VOUT). The maximum allowed power dissipation is 800mW at TA =
Current Limit
+70°C or: The MAX1818 monitors and controls the pass transistor’s PMAX = (TJ(MAX) - TA) / ( θJC + θCA) gate voltage, limiting the output current to 0.8A (typ). This current limit doubles when the output voltage is within 4% where TJ - TA is the temperature difference between the of the nominal value to improve performance with large MAX1818 die junction and the surrounding air, θJC is the load transients. thermal resistance of the junction to the case, and θCA is the thermal resistance from the case through the PC
Thermal Overload Protection
board, copper traces, and other materials to the surround- Thermal overload protection limits total power dissipation ing air. For best heatsinking, the copper area should be in the MAX1818. When the junction temperature exceeds equally shared between the IN, OUT, and GND pins. TJ = +170°C, a thermal sensor turns off the pass transis- The MAX1818 delivers up to 0.5A RMS and operates with tor, allowing the IC to cool. The thermal sensor turns the input voltages up to +5.5V, but not simultaneously. High pass transistor on again after the junction temperature output currents can only be sustained when inputoutput differential voltages are low, as shown in Figure 3. www.maximintegrated.com Maxim Integrated │ 7
