Detailed Description
The MAX25210 low-quiescent-current, high-voltage linear regulator family is ideal for use in automotive and battery-operated systems. The device operates from an input voltage of +3.5V to +36V, delivers up to 300mA of load current, and consumes only 10µA of quiescent current at no load. The input is +42V tolerant and is designed to operate under load-dump conditions. The MAX25210 can be user configured as either a fixed output voltage (+3.3V or +5V) or an adjustable output voltage using an external resistive voltage divider.
The MAX25210 features an open-drain, active-low RESET output with fixed thresholds offered at 93.5% and 87.5% of the output voltage. The RESET output remains low for a delay period of 60µs after the output voltage fault is cleared. The RESET delay can be extended with an external capacitor. The MAX25210 includes an enable input, short-circuit protection and thermal shutdown.
The SET and SETOV inputs determine the output mode. For the 5V fixed-output-voltage mode (see the 5V fixed-output circuit in
Typical Application Circuits), connect SET to GND and SETOV to OUT. For the 3.3V fixed-output-voltage mode (see the 3.3V fixed-output circuit in
Typical Application Circuits), connect SET to GND and SETOV to GND.
For the adjustable-output-voltage mode (see the adjustable output circuit in Typical Application Circuits), connect SET to IN or a voltage > 2.4V and connect SETOV to a resistive voltage divider R1 and R2 between OUT and GND. An output voltage between 0.6V and 11V can be selected using the following equation:
VOUT = VSETOV x (1 + R1/R2) where VSETOV = 0.6V and R2 should be less than or equal to 110kΩ.
In order to increase the phase margin in applications with an external resistor-divider, a feed-forward capacitor in parallel with the top resistor-divider is recommended.
The MAX25210 has four current-limit options: 400mA, 330mA, 165mA, and 88mA (typ). The output can be shorted to GND continuously without damage to the device. During a short circuit, the power dissipated across the pass transistor can quickly heat the device. When the die temperature reaches +170°C, the MAX25210 turns off the pass transistor and automatically restarts after the die temperature has cooled by 20°C.
RESET Output
The MAX25210 features an active-low, open-drain reset output. Once the monitored output voltage exceeds the reset threshold voltage, the RESET output goes low as long as the fault persists. After the fault is cleared, RESET remains low for the reset timeout period and then goes high. RESET also asserts low when ENABLE is low and during thermal shutdown. The pullup voltage on the RESET pin must be greater than 1.5V.
Timeout
The MAX25210 includes a reset timeout period adjustable input. The internal capacitance produces a 60µs default delay when TIMEOUT is left unconnected. Connect a capacitor from TIMEOUT to GND to set a higher timeout period than default. Use the following formula to determine the reset timeout capacitor:
CTIMEOUT = 0.8 x ITO x TTIMEOUT
where CTIMEOUT is in nF, ITO is in µA, and TTIMEOUT is in ms.
For example, if ITO is 1µA, CTIMEOUT must be 8nF to obtain a 10ms delay.
ENABLE is an active-high, logic-level enable input that turns the device on or off. Drive ENABLE high to turn the device on. An internal 0.25µA pulldown current keeps the MAX25210 in shutdown mode when driven by an open-drain driver, or by a three-state driver in high-impedance mode. When in shutdown, the MAX25210 consumes only 2µA (typ). ENABLE withstands voltages up to 42V, allowing it to be driven by high-input level voltages or connected to IN for always-on operation.
Thermal Protection
The MAX25210 features thermal protection. When the junction temperature exceeds +170°C, an internal thermal sensor turns off the pass transistor and allows the device to cool. The thermal sensor turns on the pass transistor again after the junction temperature cools by 20°C. This results in a cycled output during continuous thermal-overload conditions. Thermal protection protects the MAX25210 in the event of fault conditions. For continuous operation, do not exceed the absolute maximum junction temperature rating of +150°C.