MC34652EF Freescale Semiconductor, MC34652EF Datasheet - Page 12

• Manufacturer Part Number: MC34652EF
• Description: IC CTRLR HOT SWAP NEG V 16-SOIC
• Manufacturer: Freescale Semiconductor
• Type: Hot-Swap Switchr

Specifications of MC34652EF

• Applications: General Purpose
• Internal Switch(s): Yes
• Current Limit: 2.0A
• Voltage - Supply: 15 V ~ 80 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

START-UP SEQUENCE
VIN pin to the negative voltage rail and the VPWR pin to the
positive voltage rail, the 34652 keeps the Power MOSFET
turned off, deactivates the power good output signals, and
resets the retry counter. If the device is disabled, no further
activities will occur and power-up would not start. If the device
is enabled, it starts to establish an internally regulated supply
voltage required for the internal circuitry. The Power
MOSFET will stay off until the start of the charging process.
Lockout (UVLO) threshold is cleared, the 34652 checks for
external components on four pins — the UV, the ILIM , the
ICHG , and 128 μs later the OV — to set the levels of the
Undervoltage Threshold, the Overcurrent Limit, the Charging
Current Limit, and the Overvoltage Threshold, respectively.
The device also checks for external components on the
TIMER pin to decide on the Start-Up and Retry Delay Timer
value, and the device keeps checking the TIMER pin
continuously throughout the operation.
Figure
paragraph). The duration of the timer is either a default or a
user-programmable value. For undervoltage and overvoltage
faults during power up the 34652 retries infinitely until normal
input voltage is attained. If the die temperature ever
increased beyond the thermal shutdown threshold or the
device is disabled, then the start-up timer resets and the retry
counter increments. If after 10 retries the die temperature is
still high and the device is still disabled, the 34652 will not
retry again and the power in the device must be recycled or
the device must be disabled to reset the retry counter.
12
34652
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
When power is first applied to the 34652 by connecting the
After Power-ON Reset (POR) and once the Undervoltage
The device then initiates the start-up timer (Point A in
6) and checks for the start-up conditions (see next
FUNCTIONAL DEVICE OPERATION
OPERATIONAL MODES
in
Start-Up Conditions
• Input voltage is below the overvoltage turn-off threshold.
• Input voltage is above the undervoltage turn-off threshold.
• Die temperature is less than thermal shutdown
• Device is enabled.
the length of the start-up timer and the retry counter is less
than or equal to 10, the device starts to turn on the Power
MOSFET gradually to control the inrush current that charges
up the load capacitor to eventually switch on the load (Point B
Charging Process
definite amount of energy will be dissipated in the control
circuit, no matter what the control algorithm is. This energy is
equal to the energy transferred to the capacitor — ½ CV
With this in mind, the Power MOSFET in the 34652 cannot
absorb this pulse of energy instantaneously, so the pulse
must be dissipated over time. To limit the peak power
dissipation in the Power MOSFET and to spread out the
Figure
The start-up conditions are as follows:
This threshold is either a default or user-programmable
value.
This threshold is either a default or user-programmable
value.
temperature.
If the start-up conditions are satisfied for a time equal to
When charging a capacitor from a fixed voltage source, a
6).
Figure 6. Start-Up Sequence
Analog Integrated Circuit Device Data
Freescale Semiconductor
2
.