CAT6201_13 Datasheet, PDF (4/10 Pages) ON Semiconductor – 300 mA / 13 V Adjustable CMOS LDO Regulator

CAT6201, CAV6201B
Pin Function
VIN is the supply pin for both the LDO’s operation and the
load the LDO is driving. It is recommended that a 1 mF
ceramic bypass capacitor be placed between the V_IN pin and
ground in close proximity to the device. When using longer
connections to the power supply, C_IN value can be increased
without limit. The operating input voltage range is from
3.3 V to 13.5 V.
FLT is an active low open−drain output indicating one of 3
fault conditions:
1. Input under−voltage: input is below the intended
output voltage
2. Over−current. Brief over−current events are
masked by a 3 ms time delay.
CAT6201/CAV6201B will limit current anytime
the load tries to draw more than the maximum
allowed, however reporting of this event will
occur only if the event lasts longer than the delay
timer. Events terminating before the timer reaches
its full count are ignored and the timer is reset.
3. Over−temperature shutdown has occurred.
EN is an active HIGH logic level input for switching the
regulator’s output between ON and OFF. A weak internal
pull down assures that if EN pin is left open, the circuit is
disabled.
BYP controls the soft−start feature for the regulator. When
large capacitive loads are present at the regulator’s output,
enabling the regulator will produce large current surges on
the V_IN supply line. To reduce these surges the regulator can
be turned on gently by connecting a capacitor between the
BYP pin and ground. The larger the capacitance value the
more slowly V_OUT approaches its programmed value. The
table below gives a list of common capacitor values and their
resulting turn−on times. If the soft−start feature is not
desired, this pin should be left floating.
Capacitance [nF]
0
10
100
t_ON [ms]
0.2
1
10
GND is the ground reference for the LDO in the TDFN
package, center metal pad is internally connected to GND.
If electrical contact is made with this pad, it should be to
GND and/or the ground plane of the PCB. Connection to the
ground plane enhances thermal conductivity drawing heat
out of the package and into the surrounding PCB.
ILIM stands for Current Limit and is the control input for
setting the point at which the current limit is invoked. I_LIM
is defined as the current at which V_OUT is still within 80%
of its nominal value and should not be confused with I_SC, the
short circuit current, measured at V_OUT = 0 V, which is
typically 100 mA greater than I_LIM.
A resistor R_EXT placed between I_LIM and GND selects the
trip current according to a formula:
I_LIM
+
I_LIM0
)
Current_Limit_Factor(CLF)
R_EXT
(eq. 1)
I_LIM0 is the built−in minimum current limit (typically
150 mA), and CLF is a numerical value (typical 30,000
Volts) which relates the allowable load current to a
resistance value. The value of this resistor is determined by
the following equation:
R_EXT(W)
+
CLF(V)
I_LIM(A) * I_LIM0(A)
(eq. 2)
It is recommended that I_LIM be set to at least 50% higher
than the maximum intended continuous I_OUT.
Example: Set I_LIMIT = 600 mA
R_EXT(W)
+
30, 000 V
0.6 A * 0.15
A
+
68
KW
(eq. 3)
VADJ is the output voltage control pin. A resistor divider
placed between VOUT and GND whose center point
connects to VADJ sets the LDO regulator’s output voltage.
Typical VADJ value is 1.25 V. The current through the
resistor divider can be anywhere between 10 mA and 1 mA.
The higher this current is, the lower the noise.
For best performance R1 and R2 should have similar
temperature coefficients, otherwise output voltage accuracy
will be compromised.
ǒ Ǔ V_OUT + V_ADJ
1
)
R₁
R₂
(eq. 4)
VOUT is the LDO regulator output. A small 2.2 mF ceramic
bypass capacitor is required between VOUT and ground.
For better transient response, its value can be increased to
4.7 mF. This capacitor should be located near the device.
VOUT is protected against short circuits and over−temp
operation by internal circuitry. In the event of an
over−current, the LDO behaves like a current source,
limiting current at the output. The maximum current
allowed is set by R_EXT, the resistor between I_LIM and GND.
If the load attempts to draw more than the allowed current,
VOUT and IOUT decrease together and thus limit the total
power delivered.
VOUT is protected against the application of voltages
greater than VIN. For example, in automotive applications,
if CAT6201/CAV6201B is powering a remote load and
damage occurs to a wiring harness shorting a powered line,
Battery + for instance, to VOUT, CAT6201/CAV6201B will
not be damaged by this higher voltage being applied to
VOUT.
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