MIC2505 datasheet(12/24 Pages) MICROCHIP

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MIC2505/6

DS20005579A-page 12

 2016 Microchip Technology Inc.

5.0

FUNCTIONAL DESCRIPTION

The MIC2505-series and MIC2506 are high-side

N-Channel switches. The MIC2505, MIC2505-1, and

MIC2506 have active-high enable inputs. The

MIC2505-2 has an active-low input. Fault conditions

inhibit output transistor turn-on or turn-off when

enabled.

5.1

Control Input

CTL (control input) activates the oscillator, thermal

shutdown, UVLO, 1.2V reference, and gate control

circuits. If there are no fault conditions, the output

MOSFET turns on when enabled.

5.2

Reference

A 1.2V bandgap reference supplies a regulated voltage

to the thermal shutdown and undervoltage lockout

circuits. The reference is only active when CTL is

enabled.

5.3

Oscillator/Charge Pump

The oscillator produces an 80 kHz square wave output

that drives the charge pump. The oscillator is enabled

when CTL is active.

The charge pump is a voltage quintupler (5x). The

charge pump capacitors are self contained.

5.4

Gate Control

The gate control circuit charges the output MOSFET

gate from the charge pump output or discharges the

MOSFET gate to ground as determined by CTL,

thermal shutdown, or undervoltage lockout (UVLO).

An optional, external capacitor may be connected to

the MIC2505 GATE to lengthen the rise time. This

slows the turn on of the MOSFET output switch. (See

Figure 2-13) Because this pin connects directly to the

MOSFET gate, use ESD precautions when contacting

components connected to this pin. Leakage resistance

may increase turn on times.

5.5

Input and Output

IN (input) is the supply connection to the logic circuitry

and the drain of the output MOSFET. OUT (output) is

the source of the output MOSFET. In a typical circuit,

current flows through the switch from IN to OUT toward

the load.

The output MOSFET and driver circuitry are also

designed to allow the MOSFET source to be externally

forced to a higher voltage than the drain (VOUT > VIN)

when the output switch is off and VIN > UVLO minimum.

In this situation, the MIC2505/6 avoids undesirable

drain to body diode reverse current flow by grounding

the body when the switch is off. The conventional

method for optimum turn-on threshold has the source

connected to the body. This would allow a large current

to flow when VSOURCE > VDRAIN + 0.6V.

5.5.1

MIC2505 SERIES ONLY

Duplicate IN and OUT leads are not internally

connected. Connect both IN pins to the supply.

Connect both OUT leads to the load.

5.6

Thermal Shutdown

Thermal shutdown shuts off the output MOSFET and

signals the fault flag if the die temperature exceeds

135°C. 10°C of hysteresis prevents the switch from

turning on until the die temperature drops to 125°C.

Overtemperature detection functions only when the

control input is enabled (output MOSFET is on). Both

MIC2506 outputs are shut off during overtemperature,

and both flags will go low.

5.7

Undervoltage Lockout

UVLO (undervoltage lockout) prevents the output

MOSFET from turning on until VIN (input voltage)

exceeds 2.5V typical. After the switch turns on, if VIN

drops below 2.3V typical, UVLO shuts off the output

MOSFET and turns the fault flag on (active-low) until

VIN drops below 1.5V.

Undervoltage detection functions only when the control

input is enabled (output MOSFET is on).

5.8

Overcurrent Limit

The overcurrent limit is preset internally. The preset

level prevents damage to the output MOSFET, but

allows a minimum current of 2A through the output

MOSFET of the MIC2505-series and 1A for each

output MOSFET of the MIC2506. Output current is

monitored by sensing the voltage drop across the

output MOSFET drain metal resistance.

Overcurrent detection functions only when the control

input is enabled (output MOSFET is on) and VIN is

above the UVLO threshold.

5.9

Open-Load Detection

Open-load detection is available only on the MIC2505

and MIC2506. The open-load detection feature is not

included in the MIC2505-1 or -2 versions.

Open-load detection indicates the absence of an output

load by activating the fault flag. Open-load detection is

optional and is enabled by connecting a high-value

pull-up resistor between IN and OUT. If there is no load,

the circuit detects a high OUT (output) voltage (typically

≥1V) and signals the fault flag. Under normal

conditions, the low resistance of a typical load pulls

OUT low. Open-load detection functions only when the

control input is low (output MOSFET is off).

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