A8450KLB Allegro Microsystems Inc, A8450KLB Datasheet - Page 8

• 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
Buck Converter with Switching Regulator. A current-
mode, variable frequency buck DC-to-DC converter and switch-
ing regulator are integrated in the A8450, as shown in figure 2.
This feature allows the device to efficiently handle power over a
wide range of input supply levels. The DC-to-DC converter out-
puts 5.7 V typical, and has an overcurrent limit of 1.2 A typical.
The converter employs a soft-start feature. This ramps the con-
verter output voltage and limits the maximum demand on V
by controlling the inrush current required at power-on to charge
the external capacitor, COUT, and any DC load.
An internal charge pump provides gate drive for the
N-channel MOSFET buck switch. A 100% duty cycle is imple-
mented when using low V
At V
figure 3. This reduction keeps the switching frequency, f
within a reasonable range and lowers the ripple current. Lowering
the ripple current at low V
regulator headroom due to V
5 V Linear Regulators. Two 5 V medium-power linear regulators
are provided. These low-dropout regulators feature foldback current
limiting for short-to-ground protection. When a direct short is applied
to the regulator output, either V5A or V5D, the current folds back
BB
lower than 12 V, off-time, t
BB
BB
VCP
ENB
REG
input voltages.
levels prevents degradation of linear
ripple voltage.
OFF
Buck Converter
Generation
, is reduced, as shown in
Soft Start
Bandgap
Counter
1.22 V
Ramp
Clock
Figure 2. Buck converter with switching regulator
Automotive Multioutput Voltage Regulator
Functional Description
VBB
PWM
REG
1.2 A Limit
Error
,
Clamp
Switching
Regulator
Control
I
DEMAND
I
PEAK
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
Compensation
Buck Switch
5
Figure 3. When VBB falls below 12 V, t
LX
t
OFF
0.58 μs
6.02 V
D1
7
100 μH
L1
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
t
9
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
OFF
V
BB
by V
VREG
(V)
100 μF
COUT
BB
11
2.05 μs
11 V
OFF
4.75 μs
12 V
13
decreases
15
8