A8698ELJ-T Allegro Microsystems Inc, A8698ELJ-T Datasheet

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A8698ELJ-T

Manufacturer Part Number
A8698ELJ-T
Description
IC REG STEP DOWN 3A 8-SOIC
Manufacturer
Allegro Microsystems Inc
Type
Step-Down (Buck)r
Datasheet

Specifications of A8698ELJ-T

Internal Switch(s)
Yes
Synchronous Rectifier
No
Number Of Outputs
1
Voltage - Output
0.8 ~ 20 V
Current - Output
3A
Voltage - Input
8 ~ 25 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (3.9mm Width) Exposed Pad, 8-eSOIC. 8-HSOIC
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Power - Output
-
Frequency - Switching
-
Features and Benefits
▪ 8 to 25 V input range
▪ Integrated DMOS switch
▪ Adjustable fixed off-time
▪ Highly efficient
▪ Adjustable 0.8 to 20 V output
Package: 8-Lead SOIC with exposed
thermal pad (suffix LJ)
A8698-DS, Rev. 4
RTSET
30.1 k
Circuit for 12 V step down to 3.3 V at 3 A.
BOOT
ENB
TSET
GND
A8698
VBIAS
Approximate Scale 1:1
VIN
FB
LX
CBOOT
0.01 μF
D1
Wide Input Voltage 3.0 A Step Down Regulator
33 μH
L 1
82 μF
35 V
CIN3
R1
6.34 k
R2
2 k
+8 to 24 V
VOUT
3.3 V / 3 A
82 μF
35 V
CIN2
330 μF
6.3 V
ESR
COUT
Typical Application
0.22 μF
CIN1
Description
The A8698 is a constant off-time current mode step-down
regulator with a wide input voltage range. Regulation voltage is
set by external resistors, to output voltages as low as 0.8 V.
The A8698 includes an integrated power DMOS switch to
reduce the total solution footprint. It also features internal
compensation, allowing users to design stable regulators with
minimal design efforts.
The off-time can be set with an external resistor, allowing
flexibility in inductor selection. Additionally, the A8698 has
a logic level enable pin which can shut the device down and
put it into a low quiescent current mode for power sensitive
applications.
The A8698 is supplied in a low-profile 8-lead SOIC with
exposed pad (package LJ). Applications include:
▪ Applications with 8 to 25 V input
▪ Consumer electronics, networking equipment
▪ 12 V lighter-powered applications (portable DVD, etc.)
▪ Point of Sale (POS) applications
92
90
88
86
84
82
80
78
76
74
72
70
0
Efficiency curves for circuit at left.
0.5
V
V
OUT
OUT
= 2.5 V
V
= 3.3 V
1.0
Efficiency
OUT
V
IN
= 5.0 V
= 12.0 V
Load Current (A)
1.5
2.0
A8698
2.5
3.0

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A8698ELJ-T Summary of contents

Page 1

Wide Input Voltage 3.0 A Step Down Regulator Features and Benefits ▪ input range ▪ Integrated DMOS switch ▪ Adjustable fixed off-time ▪ Highly efficient ▪ Adjustable 0 output Package: 8-Lead SOIC with ...

Page 2

... Package (°C/ Additional information is available on the Allegro website. Ordering Information Use the following complete part numbers when ordering: a Part Number A8698ELJTR-T a Leadframe plating 100% matte tin. b Contact Allegro for additional packing options. Wide Input Voltage 3.0 A Step Down Regulator Symbol Conditions V ...

Page 3

A8698 BOOT V IN ENB μC TSET GND VBB UVLO TSD Wide Input Voltage 3.0 A Step Down Regulator Functional Block Diagram Boot Charge – Switch PWM Control Switch Disable Clamp + – – I_Peak I_Demand Error COMP Soft Start ...

Page 4

A8698 ELECTRICAL CHARACTERISTICS Characteristics VIN Quiescent Current VBIAS Input Current Buck Switch On Resistance Fixed Off-Time Proportion Feedback Voltage Output Voltage Regulation Feedback Input Bias Current Soft Start Time Buck Switch Current Limit ENB Open Circuit Voltage ENB Input Voltage ...

Page 5

A8698 Start-up t Power Off V t Detail: Step Up Transient Response 3 OUT 1. Wide Input Voltage 3.0 A Step Down Regulator Performance Characteristics V ; 2.00 ...

Page 6

A8698 Load Regulation 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4 0 0.5 1.0 1.5 Load Current (A) Wide Input Voltage 3.0 A Step Down Regulator 0.2 0.1 0 –0.1 –0.2 –0.3 –0.4 –0.5 –0.6 2.0 2.5 3.0 9 Line Regulation ...

Page 7

A8698 The A8698 is a fixed off-time, current-mode–controlled buck switching regulator. The regulator requires an external clamping diode, inductor, and filter capacitor, and operates in both continu- ous and discontinuous modes. An internal blanking circuit is used to filter out ...

Page 8

A8698 is the on-resistance of the switching MOSFET. R DS(on) The switching frequency is calculated as follows Shorted Load. If the voltage on the FB pin falls below 0.4 V, the regulator ...

Page 9

A8698 the connection. The R should be much larger than the feedback r resistor to prevent any potential offset in output voltage. For example < 10 kΩ, R should be 1 MΩ based on the ...

Page 10

A8698 Efficiency versus Load Current Stabilized with low ESR capacitor 100 0.5 1.0 1.5 Load Current (A) Silkscreen Layer Top and Silkscreen Layers Wide Input Voltage 3.0 A Step ...

Page 11

A8698 Evaluation Board Bill of Materials Designator Quantity C1.1 1 Ceramic chip, 22 μ ±20%, X5R. C1.2, C1.3 2 Aluminum electrolytic capacitor μF, 930 C2 1 Ceramic capacitor, X7R, ±10%, 0.1 μ ...

Page 12

A8698 Package LJ 8-Pin SOIC 8X 0.10 [.004] 8X Pin-out Diagram BOOT 1 8 VIN ENB Pad TSET 3 6 VBIAS GND (Top View) The products described herein are man u fac tured under ...

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