Datasheet

V
IN
V
OUT
STATUS
UVLO
OVP
TIMER
GND
EN
OUT
SENSE
GATE
VIN
LM5060
EN
R8
R10
R11
R
S
Q1
C1
R4
GND GND
nPGD
High = Fault, Low= OK
High = On, Low= Off
R9
LM5060
www.ti.com SNVS628F –OCTOBER 2009–REVISED APRIL 2013
Figure 21. Basic Application Circuit
Functional Description
The LM5060 is designed to drive an external high-side N-channel MOSFET. Over-Current protection is
implemented by sensing the voltage drop across the MOSFET. When an adjustable voltage drop threshold is
exceeded, and an adjustable time period has elapsed, the MOSFET is disabled. Over-Voltage Protection (OVP)
and Under-Voltage Lock-Out (UVLO) monitoring of the input line is also provided. A low state on the enable pin
will turn off the N-channel MOSFET and switch the LM5060 into a very low quiescent current off state. An active
low power good output pin is provided to report the status of the N-channel MOSFET. The waiting time before
the MOSFET is turned off after a fault condition is detected can be adjusted with an external timer capacitor.
Since the LM5060 uses a constant current source to charge the gate of the external N-channel MOSFET, the
output voltage rise time can be adjusted by adding external gate capacitance. This is useful when starting up into
large capacitive loads.
POWER-UP SEQUENCE
The basic application circuit is shown in Figure 21 and a normal start-up sequence is shown in Figure 22. Start-
up of the LM5060 is initiated when the EN pin is above the (EN
THH
) threshold (2.0V). At start-up, the timer
capacitor is charged with a 6 µA (typical) current source while the gate of the external N-channel MOSFET is
charged through the GATE pin by a 24 µA (typical) current source.
When the gate-to-source voltage (V
GS
) reaches the V
GATE-TH
threshold (typically 5V) the V
GS
sequence ends, the
timer capacitor is quickly discharged to 0.3V, and begins charging the timer capacitor with a11 µA current
source.
The timer capacitor will charge until either the V
DS
Comparator indicates that the drain-to-source voltage (V
DS
)
has been reduced to a nominal value (i.e. no fault) or the voltage on the timer capacitor has reached the V
TMRH
threshold (i.e. fault). The V
DS
Comparator monitors the voltage difference between the SENSE pin and the OUT
pin. The SENSE pin voltage is user programmed to be lower than the input supply voltage by selecting a suitable
sense resistor value. When the OUT pin voltage exceeds the voltage at the SENSE pin, the nPGD pin is
asserted low (i.e. no fault) and the timer capacitor is discharged.
STATUS CONDITIONS
Output responses of the LM5060 to various input conditions is shown in Table 1. The input parameters include
Enable (EN), Under-Voltage Lock-Out (UVLO), Over-Voltage Protection (OVP), input voltage (VIN), Start-Up
Fault (V
GS
) and Run Fault (V
DS
) conditions. The output responses are the VIN pin current consumption, the
GATE charge current, the TIMER capacitor charge (or discharge) current, the GATE discharge current if the
timer capacitor voltage has reached the V
TMRH
threshold (typically 2V), as well as the status of nPGD.
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