A8450KLB Allegro Microsystems Inc, A8450KLB Datasheet - Page 9

• Manufacturer Part Number: A8450KLB
• Description: IC REG MULTI-OUT AUTO 24-SOIC
• Manufacturer: Allegro Microsystems Inc
• Type: Step-Down (Buck)r

Specifications of A8450KLB

• Topology: Step-Down (Buck) (1), Linear (LDO) (4)
• Function: Automotive
• Number Of Outputs: 4
• Voltage/current - Output 1: 5.7V, 1.2A
• Voltage/current - Output 2: 5V, 200mA
• Voltage/current - Output 3: 5V, 200mA
• W/led Driver: No
• W/supervisor: No
• W/sequencer: Yes
• Voltage - Supply: 6 V ~ 45 V
• Operating Temperature: -40°C ~ 135°C
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• Current - Output: 200mA, 550mA
• Voltage - Output: 3.3V, 5V, 5.7V, Adj
• Voltage - Input: 6 ~ 45 V
• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -
• Frequency - Switching: -

A8450
to 0 V at 50 mA, as shown in figure 4a. The voltage recovers to its
regulated output when the short is removed.
The V5A and V5D regulators track each other during power-on, and
when the device is enabled and ramped up out of disabled mode,
the regulators will start to track when V
1.8 V. These regulators are guaranteed to track to within 0.5% of
each other under normal operating conditions.
3.3 V and Adjustable Linear Regulators. Two additional
linear regulators, one that outputs at 3.3 V, and another that has a
1.2 V to 3.3 V adjustable output, can be implemented using external
npn pass transistors. The output voltage of the adjustable regulator,
V
R2 (Ω). It can be calculated as
where V
Additional pins, CL33 and CLADJ, are provided for setting cur-
rent limits. These are used to protect the external pass transis-
tors from a short-to-ground condition. The current limit setting,
I
CL
OUTVADJ
(mA), is calculated using the formula
Figure 4a. Linear foldback to 50 mA. Foldback occurs at the typical
current limit for the 5 V regulator.
FB
6
5
4
3
2
1
0
(V), is set by the values of the output resistors, R1 and
(V) is the voltage on the feedback pin, FB.
0
50
V
5V Regulators Overcurrent Foldback
OUTVADJ
100
I
CL
= V
= V
OC
150
I
FB
OUT
I
OUTV5DLIM
⁄ R
(1+R1 ⁄ R2)
(mA)
RCL
200
REG
and I
reaches approximately
OUTV5ALIM
250
Automotive Multioutput Voltage Regulator
300
1600
Figure 4b. Linear foldback to a percentage of I
the current limit setting for the regulator.
where RCL (Ω) is the current-limiting resistor corresponding to
that regulator (R3 for the 3.3 V regulator, and R4 for the adjustable
regulator). When I
that regulator is folded back to 40% of I
4b. If current limiting is not needed, the CL33 and CLADJ pins
should be shorted to the VREG pin.
Disabled Mode. When the two input signal pins, ENBAT and
ENB, are pulled low, the A8450 enters disabled mode. This is a
sleep mode, in which all internal circuitry is disabled in order to
draw a minimal current from VBB. When either of these pins is
pulled high, the device is enabled. When emerging from disabled
mode, the buck converter switching regulator does not operate
until the charge pump has stabilized (≈ 300 μs).
Enabled Mode. When one or both of the signal input pins,
ENBAT and ENB, are in the high state, the A8450 is enabled.
ENBAT is an edge-triggered enable (logic 1 ≥ 2.7 V), which is
used to enable the A8450 in response to a high-voltage signal,
such as from an automobile ignition or battery switch. In this
capacity, ENBAT is used only as a momentary switch to wake up
the device. If there is no need for a high-voltage signal, ENBAT
can be pulled low continuously.
ENB is used to initiate the reset of the device. If ENBAT is pulled
6
5
4
3
2
1
0
0
3.3 V and Adjustable Regulators Overcurrent Foldback
V
OUTVADJ(min)
V
OUTV33
CL
is exceeded, the maximum load current through
and V
0.4 I
OUTVADJ(max)
I
CL
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
OUT
±10%
(mA)
CL
CL
±10%, as shown in figure
. Foldback occurs at
I
CL
1600
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