34652 datasheet(15/26 Pages) FREESCALE

15 / 26 page

Analog Integrated Circuit Device Data

Freescale Semiconductor

34652

FUNCTIONAL DEVICE OPERATION

PROTECTION FEATURES

BOARD REMOVAL

When the board is removed, its power ramps down. As

soon as the 34652’s input voltage reaches the undervoltage

turn-off threshold, the undervoltage detection circuit activates

and the Power MOSFET turns off for having violated one of

the start-up conditions (list on page 12).

34652 STATE MACHINE DIAGRAM

Figure 13 is a representation of the 34652 behavior in

different modes of operation.

Figure 13. State Diagram

PROTECTION FEATURES

UNDERVOLTAGE

When the voltage on the UV pin drops below the

undervoltage falling threshold for more than 1.0 ms, an

undervoltage fault is detected and one of the start-up

conditions (list on page 12) is violated. The 34652 turns off

the Power MOSFET and deactivates the power good output

signals, disabling the load (Point A in Figure 14). The 34652

stays in this state until the voltage on the UV pin rises above

the undervoltage rising threshold for more than 1.0 ms,

signaling that the supply voltage is in the normal operation

range (Point B in Figure 14). Then a new start-up sequence

initiates as described on page 12. The undervoltage

detection circuit is also equipped with a 1.0 V hysteresis

when in default mode. The hysteresis value depends on the

undervoltage detection threshold and can be calculated as

follows:

VUVHY = VUV(RISING) * [1 - (1.3 V - VUVCHY) / 1.3 V]

Figure 14. Undervoltage Fault Followed by a

New Start-Up Sequence

MOSFET

→ OFF

PG = 0

Undervoltage

MOSFET

→ OFF

PG = 0

Power Off

Temp < 135°C

Filter = 12

µs

VPWR < VUVLOF

Filter = 1.0 ms

A signal “set” is generated to check

resistors on UV, ILIM, ICHG, and

TIMER pins and 128

µs later

the OV pin

Retry Fault

STOP

Toggle DISABLE

or cycle Power Off

then On to clear fault

Power

Good Check

and VDS < 500 mV

for 20 ms

Charging Mode

≤ 10

Turn Off

MOSFET

→ OFF

PG = 0

PG = 1

N = 0

VPWR > VUVLOR

Filter = 1.0 ms

Filter = 3.0 ms

ILOAD > ILIM

ILOAD < ILIM - ILIMHY

Short Circuit

Detection

Fast Gate Discharge

< 10

µs

ILOAD > ISHORT

Overcurrent

for > 3.0 ms

Pass PG

Check

Fail PG

Check

> 10

for 100

µs

VPWR < VUV(OFF)

Filter = 1.0 ms

MOSFET

→ OFF

PG = 0

Overvoltage

VPWR < VOV(ON)

VPWR > VOV(OFF)

Filter = 1.0 ms

PG = 0

MOSFET

→ OFF

Temp > 160°C

Filter = 12

µs

Thermal

Shutdown

Ext. Resistor Check

POR is generated

N = 0

MOSFET

→ OFF

PG = 0

DISABLE

POR is generated

N = 0

DISABLE = 1

Filter = 1.0 ms

DISABLE = 0

Filter = 1.0 ms

VPWR > VUV(ON)

Filter = 1.0 ms

If ILOAD < ILIM

Overcurrent Mode

Normal Operation

VDS < 500 mV

Start-Up Conditions

• Thermal Shutdown < 160°C

Filter = tTIMER

• VPWR > VUV(OFF)

• VPWR < VOV(OFF)

N = N + 1

• DISABLE = 0

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