MP5098

– 12V/5V, DUAL-CHANNEL E-FUSE WITH CURRENT MONITORING

MP5098 Rev. 1.0

MonolithicPower.com

16

11/2/2021

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© 2021 MPS. All Rights Reserved.

OPERATION

The MP5098 is a 12V/5V, dual-channel e-fuse

with current limiting. It is designed to limit the

inrush current to the load while a circuit card is

inserted into a live backplane power source.

This limits

the backplane’s voltage drop and the

dV/dt to the load. The MP5098 offers an

integrated solution that can monitor the input

voltage (VIN), output voltage (VOUT), output

current

(IOUT),

and

die

temperature.

This

eliminates the need for an external current-

sense resistor, power MOSFET, and thermal-

sensing device.

Under-Voltage Lockout (UVLO) Protection

Channel 1 can be used in the 12V system, and

channel 2 can be used in the 5V system. High

energy transients can occur during normal

operation or hot swap. These transients are

determined by the

wire’s parasitic inductance

and resistance, as well as the VCC capacitor

(CVCC). If a power-clamped TVS diode is not

used, then the e-fuse should be able to

withstand the transient voltage. The MP5098

integrates a high-voltage MOSFET and a high-

voltage circuit at VCC to guarantee safe

operation.

If VIN drops below the under-voltage lockout

(UVLO) threshold, then the output is disabled.

Once VIN exceeds the UVLO threshold, the

output is enabled.

Soft Start (SS)

Connect a capacitor to the SS pin to set the

soft-start time (tSS). tSS is a function of the soft-

start capacitor (CSS). A constant-current source

charges CSS, and the SS voltage (VSS) ramps

up. VOUT ramps up at a similar slew rate to VSS.

tSS can be calculated with Equation (1):

( )

( )

SS

SS

DT

DV

I

nF

C

V

ms

t



=

1

/

(1)

Where tDV/DT is tSS between 0% and 100% of

VOUT, and ISS is the soft-start current.

Output Over-Voltage Protection (OVP)

The

MP5098

provides

output

over-voltage

protection (OVP) to protect the downstream

load from surge voltages at the input. An

accurate, fast comparator monitors VOUT. If VOUT

exceeds the OVP threshold, then the gate

voltage (VGATE) of the internal MOSFETs is

pulled down. VGATE is regulated at a certain

value to keep VOUT clamped at the OVP

threshold. Fast loop response speed (typically

2µs) reduces the over-voltage (OV) overshoot.

Over-Current Protection (OCP)

If an over-current (OC) fault occurs (e.g. the

load exceeds the current limit [ILIMIT_CHx] or a

short

occurs),

then

over-current

protection

(OCP) is triggered and the part enters constant-

current mode. If the OC condition remains after

150µs, then the part enters hiccup mode and

shuts down. After a 200ms off time (tOFF), the

part starts up again. The MP5098 repeats this

operation until the OC condition has been

removed.

Channel

1’s current limit (ILIMIT_CH1) is set at 4A

internally,

and

its

constant-current

limit

(ILIMIT_CC_CH1) is set at 2.5A. Channel 2’s current

limit (ILIMIT_CH2) is set at 3A internally, and its

constant-current limit (ILIMIT_CC_CH2) is set at 1.3A.

Current Monitoring

The MP5098 provides current monitoring for

both channel 1 and channel 2. The IMONx pin

generates a current proportional to channel 1

and channel 2’s load current (ILOAD_CHx).

Connect a resistor to IMONx to generate the

current monitor voltage (VIMONx). The effective

VIMONx range is between 0V and 2.5V to

guarantee that the sensing results are linear.

VIMONx can be calculated with Equation (2):

VIMONx(mV) = GIMONx x IOUT(A) x RIMONx(kΩ)

+ IOSSFET_CHx x RIMONx(kΩ)

(2)

Where GIMON_CHx is the current-sense gain,

RIMON_CHx is the current-sense resistor, and

IOFFSET_CHx is the current-sense offset.

Short Circuit Protection (SCP)

If the ILOAD_CHx increases rapidly due to a short

circuit, the current may exceed ILIMIT_CHx before

the control loop can respond. If the current

reaches the secondary ILIMIIT level (8A), then

short-circuit protection (SCP) is triggered and

the fast turn-off circuit turn offs the MOSFET

(see Figure 1 on page 15). This limits the peak

current through the MOSFET to maintain VIN.

The total short-circuit response time is less than