ST STEF12 User Manual

Features

■ Continuous current (typ): 3.6 A

■ N-channel on-resistance (typ): 53 mΩ

■ Enable/Fault functions

■ Output clamp voltage (typ):15 V

■ Undervoltage lockout

■ Short-circuit limit

■ Overload current limit

■ Controlled output voltage ramp

■ Thermal latch (typ): 165 °C

■ Uses tiny capacitors

■ Operating junction temp. - 40 °C to 125 °C

■ Available in DFN10 (3x3 mm) package

Applications

■ Hard disk drives

■ Solid state drives (SSD)

■ Hard disk and SSD arrays

■ Set-top boxes

■ DVD and Blu-ray disc drivers

Description

The STEF12 is an integrated electronic fuse
optimized for monitoring output current and input
voltage. Connected in series to a 12 V rail, it is
capable of protecting the electronic circuitry on its
output from overcurrent and overvoltage. The
device has a controlled delay and turn-on time.
When an overload condition occurs, the STEF12
limits the output current to a predefined safe
value. If the anomalous overload condition

STEF12

Electronic fuse for 12 V line

Datasheet − production data

DFN10 (3x3 mm)

persists it goes into an open state, disconnecting
the load from the power supply. If a continuous
short-circuit is present on the board, when power
is re-applied the E-fuse initially limits the output
current to a safe value and then again goes into
an open state. The device is equipped with a
thermal protection circuit. The intervention of the
thermal protection is signalled to the board
monitoring circuits through a signal on the Fault
pin. Unlike the mechanical fuses, which must be
physically replaced after a single event, the E­fuse does not degrade in its performance after
short-circuit/thermal protection interventions and
it is reset either by recycling the supply voltage or
using the Enable pin. The companion chip for the
5 V power rails is also available with part number
STEF05.

Table 1. Device summary

Order code Package Packaging

STEF12PUR DFN10 (3x3 mm) Tape and reel

March 2012 Doc ID 019056 Rev 4 1/20

This is information on a product in full production.

www.st.com

20

Contents STEF12

Contents

1 Device block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Typical application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.1 Operating modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.1.1 Turn-on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5.1.2 Normal operating condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.1.3 Output voltage clamp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.1.4 Current limiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.1.5 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.2 R limit calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

5.3 C

5.4 Enable/Fault pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

dv/dt

6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

7 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2/20 Doc ID 019056 Rev 4

STEF12 Device block diagram

1 Device block diagram

Figure 1. STEF12 block diagram

AM09891v1

Doc ID 019056 Rev 4 3/20

Pin configuration STEF12

2 Pin configuration

Figure 2. Pin configuration (top view)

GND
dv/dt

V

En/fault

CC

I-Limit

N/C

AM09880v1

Table 2. Pin description

Pin n° Symbol Note

1 GND Ground pin

The internal dv/dt circuit controls the slew rate of the output voltage at turn-on. The

2dv/dt

3 En/Fault

internal capacitor allows a ramp-up time of around 1ms. An external capacitor can be
added to this pin to increase the ramp time. If an additional capacitor is not required, this
pin should be left open.

The Enable/Fault pin is a tri-state, bi-directional interface. During normal operation the pin
must be left floating, or it can be used to disable the output of the device by pulling it to
ground using an open drain or open collector device.

If a thermal fault occurs, the voltage on this pin goes into an intermediate state to signal a
monitor circuit that the device is in thermal shutdown. It can be connected to another
device of this family to cause a simultaneous shutdown during thermal events.

Source
Source
Source
Source
Source

4 I-Limit

5 NC Not connected

6 to 10 V

11 V

4/20 Doc ID 019056 Rev 4

OUT

/Source

CC

A resistor between this pin and the Source pin sets the overload and short-circuit current
limit levels.

Connected to the source of the internal power MOSFET and to the output terminal of the
fuse

Exposed pad. Positive input voltage must be connected to VCC.

STEF12 Maximum ratings

3 Maximum ratings

Table 3. Absolute maximum ratings

Symbol Parameter Value Unit

V

CC

/source (max 100ms) -0.3 to Vcc+0.3 V

V

OUT

Positive power supply voltage (max 100ms) -0.3 to 25

V

I-Limit (max 100ms) -0.3 to 25 V

En/Fault -0.3 to 7 V

dv/dt -0.3 to 7 V

Positive power supply voltage (steady state) -0.3 to 18

T

op

T

STG

T

LEAD

1. The thermal limit is set above the maximum thermal rating. It is not recommended to operate the device at temperatures
greater than the maximum ratings for extended periods of time.

Operating junction temperature range

Storage temperature range -65 to 150 °C

Lead temperature (soldering) 10 sec 260 °C

(1)

-40 to 125 °C

Note: Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these conditions is not implied.

Table 4. Thermal data

Symbol Parameter Value Unit

R

R

thJA

thJC

Thermal resistance junction-ambient 52.7 °C/W

Thermal resistance junction-case 17.4 °C/W

Table 5. ESD performance

Symbol Parameter Test conditions Value Unit

HBM 1 kV

ESD ESD protection

Doc ID 019056 Rev 4 5/20

MM 200 V

CDM 500 V

Electrical characteristics STEF12

4 Electrical characteristics

VCC = 12 V, V

= 3.3 V, CI = 10 µF, CO = 47 µF, TJ = 25 °C (unless otherwise specified).

EN

Table 6. Electrical characteristics for STEF12

Symbol Parameter Test Conditions Min. Typ. Max. Unit

Under/Overvoltage protection

V

Clamp

V

UVLO

V

Hyst

Power MOSFET

t

dly

R

DSon

V

OFF

I

Current limit

Output clamping voltage VCC = 18 V 13.8 15 16.2 V

Undervoltage lockout Turn-on, voltage rising 7.7 8.5 9.3 V

UVLO hysteresis 0.80 V

Delay time

On-resistance

Off state output voltage VCC = 18 V, V

Continuous current

D

Enabling of chip to I
with a 1 A resistive load

(1)

- 40 °C < TJ < 125 °C

GS

2

0.5in

pad, TA = 25 °C

Minimum copper, TA = 80 °C 1.7

= 100 mA

D

350 µs

35 53 70

(2)

= 0, RL = infinite 40 100 mV

(1)

3.6

82

mΩ

A

I

Short

I

Lim

Short-circuit current limit R

Overload current limit R

dv/dt circuit

dv/dt Output voltage ramp time

Enable/Fault

V

V

V

I(MAX)

V

I(INT)

I

Low level input voltage Output disabled 0.35 0.58 0.81 V

IL

Intermediate level input voltage Thermal fault, output disabled 0.82 1.4 1.95 V

High level input voltage Output enabled 1.96 2.64 3.3 V

IH

High state maximum voltage 3.4 4.3 5.4 V

Low level input current (sink) V

IL

High level leakage current for

I

I

external switch

Maximum fan-out for fault signal

Total device

I

Bias

Bias current

= 22 Ω 3.3 4.4 5.5 A

Limit

= 22 Ω 4.4 A

Limit

Enable to V
C

dv/dt

= 0 V -10 -30 µA

Enable

V

= 3.3 V 1 µA

Enable

= 11.7 V, No

OUT

0.5 0.9 2.6 ms

Total numbers of chips that can
be connected to this pin for
simultaneous shutdown

Device operational 1.5 2

Thermal shutdown 1

3Units

mA

6/20 Doc ID 019056 Rev 4