ETC BCT1583S

BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
GENERAL DESCRIPTION
The BCT1583S is a step down monolithic regulator with a built in internal power
MOSFET, capable of driving up to 3A continuous output current with excellent line and
load regulation. The output voltage can be set from 1.22 to 18V.
Requiring a minimum number of external components, it offers simple to use, but high
efficiency and advanced protection features including pulse-by-pulse current limiting and
thermal shutdown. Adjustable soft-start reduces the stress on the input source at turn-on
and the regulator draws only 20uA in shutdown mode.
BCT1583S is available in a Pb-Free SOIC8 with Exposed Pad package.
FEATURES
APPLICATIONS
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Wide Vin Range: 4.5 to 20V
3A Output Current
High Efficiency up to 95%
Output Adjustable from 1.22 to 18V
385KHz Fixed Frequency internal oscillator
20uA Shutdown Mode
Pulse-to-Pulse Over Current Protection
Thermal Shutdown
• Automatic Soft Start
• Compact SOIC8 with Exposed Pad
Simple High Efficiency Step-down
Consumer: TV, STB, DVD, VCR
Car Audio/TV/Navigation
Battery Charger
Pre-Regulator for Linear
Regulators
Typical Application
INPUT
OUTPUT
BCT1583S .2/2007
Ver 1.1
Page 1
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Pin Assignment
Pin Descriptions
Pin #
Pin Name
1
BS
High Side Gate Drive Boost Input
2
IN
Power Input
3
SW
4
GND
5
FB
6
COMP
7
EN
Enable Input (H: Step-down Operation, L: All circuits deactivated)
8
SS
Soft Start Control Input
BCT1583S .2/2007
Description
Power Switching Output
Ground
Feedback Input
Compensation Node
Ver 1.1
Page 2
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Block Diagram
Absolute Maximum Specifications
Rating
Symbol
Value
Unit
Supply Voltage Range
VIN
-0.3 to 28
Volts
Switch Voltage Range
VSW
-1 to VIN+0.3
Volts
Boost Voltage Range
VBS
Vsw-0,3 to Vsw+6
Volts
-0.3 to 6
Volts
All Other Pins
Storage Temperature Range
TSTR
-65 to 150
0
Maximum Operating Junction Temp
TJ
150
0
BCT1583S .2/2007
C
C
Ver 1.1
Page 3
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Recommended Operating Ratings
Rating
Symbol
Value
Unit
Supply Voltage Range
VIN
-4.5 to 20
Volts
Ambient Operating Temperature
TOP
-40 to 85
0
C
Electrical Specifications
0
All electrical specifications are specified at TAMBIENT = 25 C, VIN = 12V, unless otherwise specified.
Symbol
Parameter
Test
Conditions
Shutdown Supply
Current
VEN=0V
20
µA
Supply Current
VEN=4V
1.0
mA
Feedback Voltage
VFB
(Simulated over all corners and
temperature)
AEA
Error Amplifier
Voltage Gain
GEA
Error Amplifier
Transconductance
RDS(ON)1
RDS(ON)2
4.5V VIN 20V
Min
1.150
Typ
1.222
Max
1.290
Unit
V
1000
V/V
800
µA/V
High Side Switch-On
Resistance
100
m
Low Side Switch-On
Resistance
10
High Side Switch
Leakage Current
∆ICOMP = ±10µA
VEN=0V,
VSW=0V
0
10
µA
Upper Switch
Current Limit
5.5
A
GCS
Current Sense to
COMP
Transconductance
3.8
A/V
FOSC1
Oscillation Frequency
385
KHz
BCT1583S .2/2007
Ver 1.1
Page 4
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
FOSC2
Short Circuit
Oscillation Frequency
VFB=0V
40
KHz
DMAX
Maximum Duty Cycle
VFB=1.0V
90
%
DMIN
Minimum Duty Cycle
VFB=1.5V
EN Threshold Voltage
%
3.1
V
EN Pull-up Current
VEN=0V
1.9
µA
Under-Voltage
Lockout Threshold
Rising VIN
3.4
V
600
mV
10
mS
Under-Voltage
Lockout Threshold
Hysteresis
Soft Start Period
Thermal Shutdown
BCT1583S .2/2007
0
CSS=0.1µF
160
0
C
Ver 1.1
Page 5
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Performance Characteristics
Soft Start
VIN/VOUT = 12V/5V at Load Current 2A
VIN/VOUT = 12V/5V with a 1uF cap
Load Transient Waveform
Turn Off Waveform
VIN/VOUT = 12V/5V, 1A-2A Step
VIN/VOUT = 12V/5V at Load Current 2A
Efficiency at VIN/VOUT = 5.0V/1.8V
Efficiency at VIN/VOUT = 10V/5.0V
100%
95%
90%
85%
80%
75%
70%
65%
60%
55%
50%
E fficiency
Efficiency
Switching Waveforms ( VOUT & VSW)
0
0.5
1
1.5
Load Current (A)
BCT1583S .2/2007
2
2.5
3
100%
95%
90%
85%
80%
75%
70%
65%
60%
55%
50%
0
0.5
1
1.5
2
Load Current (A)
Ver 1.1
Page 6
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Typical Application Circuits
U 2 -B
EN
C8
100 nF
R1
10 k
U1
C5
1 uF
U 2 -D
VIN
C2
470 uF
C4
100 nF
BS
SS
IN
EN
COMP
SW
C1
10 nF
U 2 -C
U 2 -A
GND
C9
10 nF
FB
R4
15 k
C 10
180 pF
R3
15 k
R5
6 .8 k
U 3 -A
L1
22 uH
J2
D1
30 BQ 040
U 3 -C
U 3 -B
C 12
470 uF
VOUT
R6
C7
100 nF
R7
R8
R9
R 10
R 11
U 3 -D
*R6 - R11 = OPEN
GND
Figure 1: VIN = 5V, VOUT = 1.8V, IOUT = 0A~3A
U 2 -B
EN
R1
80 .6 k
U 2 -D
R2
51 k
C2
100 nF
VIN
C3
470 uF
C4
100 nF
C1
10 nF
U1
BS
SS
IN
EN
SW
GND
U 2 -C
U 2 -A
COMP
C9
10 nF
FB
R4
15 k
C 10
100 pF
R3
10 k
R5
47 k
U 3 -A
L1
22 uH
D1
30 BQ040
U 3 -C
U 3 -B
J2
C 12
470 uF
C7
10 nF
VOUT
R6
GND
R7
R8
R9
R 10
R 11
U 3 -D
*R6 - R11 = OPEN
Figure 2: VIN = 12V, VOUT = 5.0V, IOUT = 0A~3A
BCT1583S .2/2007
Ver 1.1
Page 7
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Configuration Table
VOUT
R5
R3
C9
L1
1.8 V
2.5 V
3.3 V
5V
12 V
7.15 kΩ
15.4 kΩ
26.1 kΩ
46.4 kΩ
133 kΩ
3 kΩ
3.9 kΩ
5.6 kΩ
7.5 kΩ
10 kΩ
4.7 nF
5.6 nF
8.2 nF
10 nF
3.3 nF
4.7 µH
4.7 – 6.8 µH
6.8 – 10 µH
10 – 15 µH
15 – 22 µH
Design Note
1. The voltage divider network formed by R4 and R5 sets the output voltage regulation point. It is
calculated by the equation below:
R5
R4 ⋅
VOUT − VREF
Where: VREF = 1.22 V
VREF
From this equation the closest standard (E48) resistance values were chosen. VOUT can be
further trimmed by adding a resistor across R5. Metal film resistors with 1% or less tolerance
are recommended.
2. The EN pin provides an enabling feature and has the following turn-on/off characteristic:
ON Threshold
OFF Threshold
= 3.1 V
= 0.7 V
To avoid intermittent turn-on/off, an Under Voltage Lock Out (UVLO) function is implemented by
R1 & R2. VINuvlo is the selected turn-on threshold of the device. Use this formula:
VIN uvlo
BCT1583S .2/2007
1+
R1
R2
⋅ VEN
Where: VEN = 3.1 V
Ver 1.1
Page 8
BlueChips Technology
A premier Mixed Signal Product Company
BCT1583S
3A Step Down
DC/DC Converter
Package Information: SO8 (Exposed Pad)
SYMBOL
A
A1
A2
b
c
D
D1
E
E1
E2
e
L
BCT1583S .2/2007
MIN (Millimeter)
MAX (Millimeter)
1.350
1.750
0.050
0.150
1.350
1.550
0.330
0.510
0.170
0.250
4.700
5.100
3.202
3.402
3.800
4.000
5.840
6.240
2.313
2.513
1.270 (BSC)
0.400
1.270
0o
8o
Ver 1.1
Page 9
BlueChips Technology
BCT1583S
3A Step Down
DC/DC Converter
A premier Mixed Signal Product Company
Marking Notation
1583S
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IC Part Number
Date Code: yyww
Sales Offices
Malaysia
Hong Kong
BCT Technology Bhd (HQ)
BlueChips Technology Pte Ltd
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All Rights Reserved.
Specifications are subject to changes without notification.
@ Copyright 2005 BlueChips Technology, Silicon Solutions Division
www.bluechipstech.com
BCT1583S .2/2007
Ver 1.1
Page 10