34652_07 Datasheet, PDF (15/26 Pages) Freescale Semiconductor, Inc – 2.0 A Negative Voltage Hot Swap Controller with Enhanced Programmability

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.
Temp > 160°C
Filter = 12 µs
Thermal
Temp < 135°C
Filter = 12 µs
Shutdown
MOSFET → OFF
PG = 0
V_PWR > V_OV(OFF)
Filter = 1.0 ms
V_PWR < V_OV(ON)
Filter = 1.0 ms
Overvoltage
MOSFET → OFF
PG = 0
V_PWR < V_UV(OFF)
Filter = 1.0 ms
V_PWR > V_UV(ON)
Filter = 1.0 ms
Undervoltage
MOSFET → OFF
PG = 0
Start-Up Conditions
• Thermal Shutdown < 160°C
• DISABLE = 0
N=N+1
• V_PWR < V_OV(OFF)
• V_PWR > V_UV(OFF)
Filter = t_TIMER
N > 10
N ≤ 10 _{Charging Mode} ^VDS ^{< 500 mV}
Turn Off
MOSFET → OFF
PG = 0
Retry Fault
STOP
Toggle DISABLE
or cycle Power Off
then On to clear fault
Fail PG
Check
Pass PG
Check
Power
Good Check
If I_LOAD < I_LIM
and V_DS < 500 mV
for 20 ms
Overcurrent
for > 3.0 ms
I_LOAD > I_LIM
for 100 µs
Ext. Resistor Check
A signal “set” is generated to check
resistors on UV, ILIM, ICHG, and
TIMER pins and 128 µs later
the OV pin
Normal Operation
PG = 1
N=0
Overcurrent Mode
Filter = 3.0 ms
I_LOAD < I_LIM - I_LIMHY
V_PWR > V_UVLOR
Filter = 1.0 ms
Power Off
MOSFET → OFF
PG = 0
N=0
POR is generated
DISABLE = 0
Filter = 1.0 ms
DISABLE
MOSFET → OFF
PG = 0
N=0
POR is generated
I_LOAD > I_SHORT
Short Circuit
Detection
Fast Gate Discharge
< 10 µs
V_PWR < V_UVLOF
Filter = 1.0 ms
DISABLE = 1
Filter = 1.0 ms
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:
V_UVHY = V_{UV(RISING) *} [1 - (1.3 V - V_UVCHY) / 1.3 V]
Figure 14. Undervoltage Fault Followed by a
New Start-Up Sequence
Analog Integrated Circuit Device Data
Freescale Semiconductor
34652
15