MC34652EF Freescale Semiconductor, MC34652EF Datasheet - Page 22

• 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

OVERCURRENT LIMIT
load and compares (with a hysteresis) the current going
through a Sensor MOSFET with a reference current value
generated in reference to the current limit value I
current going through the Sensor MOSFET becomes larger
than the reference current for more than 100 μ s, the
overcurrent signal is asserted, the gate of the Power
MOSFET is discharged fast (in less than 10 μ s) to try to
regulate the current, and the 34652 is in overcurrent mode for
3.0 ms
overcurrent mode, the device turns off the Power MOSFET
and deactivates the power good output signals. The 34652
then initiates another start-up timer and goes back through
the enhancement process. If during the 3.0 ms timer the fault
was cleared where the load current was less than I
the hysteresis value, which is 12% of I
34652 goes back to the normal operation mode and the
power good output signals stay activated. This way the
device overcomes temporary overcurrent situations and at
the same time protects the load from more severe
overcurrent situations.
there is any external resistor connected to the ILIM pin. If
there is, it determines the value of the overcurrent limit. If
there is not, it uses the default overcurrent limit value of 1.0 A.
It then uses the Sensor MOSFET to monitor the load for any
overcurrent conditions during operation as explained in the
previous paragraph.
Choosing the External Resistor R
(R
Figure
22
34652
TYPICAL APPLICATIONS
Figure 22. Charging Current External Capacitor (C
ILIM
When in normal operation mode, the 34652 monitors the
When the device passes the UVLO threshold, it checks if
The user can change the current limit by adding a resistor
220
200
180
160
140
120
100
) between the ILIM and VIN pins, as shown in
80
60
40
20
Versus Charging Current Rise Time (t
.
19,
0
If after a 3.0 ms filter time the device is still in
0
page
1
18. This way the 34652 device is adaptable
2
3
4
TICHGR (m s)
t
ICHGR
ICHG = 0.05 A
I
CHG
ICHG = 0.1 A
5
I
CHG
ICHG = 0.5 A
I
CHG
(ms)
6
ILIM
LIM
Value
7
value, then the
8
ICHGR
LIM
9
LIM
. If the
10 11
)
minus
ICHG
)
default value of 1.0 A.
resistor value to the actual value be chosen.
to different requirements and operating environments. The
overcurrent value ranges between 0.35 A and 2.25 A, with a
different values of I
versus I
following equations:
Table 9. R
Note Accuracy requirements are application dependent.
To calculate the value of the R
Figure 23. External Resistor (R
I
LIM
0.35
400
350
300
250
200
150
100
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
50
LIM
(A)
0
0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
. It is recommended that the closest 1% standard
ILIM
I
R
LIM
ILIM
(A) = 129 / [ R
Values for Some Desired I
Current Limit Value (I
(k Ω ) = [ 129 / I
R
LIM
ILIM
367.65
321.52
256.93
213.88
183.12
160.06
142.12
127.77
116.02
106.24
97.96
90.86
Table 9
and
Analog Integrated Circuit Device Data
(kΩ)
Figure 23
ILIM (A)
ILIM
lists examples of R
LIM
ILIM
(k Ω ) + 1.4 k Ω ]
I
Freescale Semiconductor
LIM
(A)] - 1.4 k Ω
2.25
1.5
1.6
1.7
1.8
1.9
2.0
2.1
2.2
—
—
—
shows a plot of R
resistor we use the
ILIM
(A)
LIM
) Value Versus
)
LIM
Values
R
ILIM
ILIM
84.71
79.33
74.58
70.36
66.58
63.18
60.11
57.31
56.01
—
—
—
(kΩ)
for
ILIM