SS6896 [SSC]
1.4MHz Current-Mode Step-Up DC/DC Converter; 1.4MHz的电流模式升压型DC / DC转换器
| 型号： | SS6896 |
| 厂家： | 
SILICON STANDARD CORP. |
| 描述： | 1.4MHz Current-Mode Step-Up DC/DC Converter |
| 文件： | 总12页 (文件大小：464K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SS6896
1.4MHz Current-Mode Step-Up DC/DC Converter
Features
Description
l Fixed-frequency 1.4MHz Current-Mode PWM
The SS6896 is
a
current-mode pulse-width
operation.
modulation (PWM), step-up DC/DC converter. The
built-in high-voltage N-channel MOSFET allows the
SS6896 to support applications with up to 30V output
voltage, as well as Single-Ended Primary Inductance
Converters (SEPIC) and other low-side switching
DC/DC converters.
l Adjustable output voltage up to 30V.
l Guaranteed 13V/ 200mA output with 5V Input.
l Input Range 2.5V to 10V.
l Maximum 0.1µA shutdown current.
l Programmable soft-start.
l Works with tiny inductors and capacitors
l Space-saving SOT-23-6 package.
The high switching frequency (1.4MHz) permits the
use of small external components. The soft-start
function is programmable with an external capacitor,
which sets the input current ramp rate.
Applications
l White LED Backlight.
l OLED Driver.
The SS6896 is available in a space-saving SOT-23-6
package.
Typical Application Circuits
86
84
82
80
78
76
74
72
L
D1
V
IN
3.3V or
4.2V
CH521S-30
ZD1
BZV55-B12
11.8V~12.2V
C3
C1
m
4.7 F
m
1 F
V
=4.2V
IN
SS6896
V
IN
=3.3V
1
3
6
4
IN
LX
SHDN FB
OFF ON
R2
SS
GND
2
I
LED
m
L: GTSK-51-150M (15 H)
L: GTSK-51-100M (10 H)
W
1K
5
70
68
R1
m
C2
2
4
6
8
10
12
14
16
18
20
m
0.033 F
LED Current (mA)
Fig. 1 Li-Ion Powered Driver for three white LEDs
L
D1
V
IN
80
3.6V or
4.2V
CH521S-30
C3
78
76
74
72
70
68
C1
ZD1
BZV55-B24
23.5V~24.5V
1mF
m
4.7 F
SS6896
1
3
6
4
V =4.2V
IN
LX
IN
V =3.6V
IN
ON
SHDN FB
OFF
R2
SS
GND
2
I
LED
66
64
62
60
1KW
5
m
L: GTSK-51-150M (15 H)
R1
C2
0.033mF
m
L: GTSK-51-100M (10 H)
2
4
6
8
10
12
14
16
18
20
LED Current (mA)
Fig. 2 Li-Ion Powered Driver for six white LEDs
Rev.2.01 6/06/2003
www.SiliconStandard.com
1 of 12
SS6896
Ordering Information
Pin Configuration
SS6896CXXX
SOT-23-6 (CG)
FRONT VIEW
1: LX
2: GND
3: FB
6
5
4
PACKING TYPE
TR: TAPE & REEL
BG: BAG
4: SHDN
5: SS
PACKAGE TYPE
G: SOT-23-6
1
2
3
6: IN
Example: SS6896CGTR
à in SOT-23-6 package in tape and reel.
l SOT-23-6 Marking
Part No.
Marking
SS6896CG
1896
Absolute Maximum Ratings
LX to GND
-0.3V to +33V
-0.3V to +6V
-0.3V to +11V
-0.3V to +6V
0.6A
FB to GND
IN, SHDN
SS to GND
LX Pin RMS Current
Continuous Power Dissipation (T = +70°C) (Note 1)
A
6-Pin SOT23 (derate 9.1mW/°C above +70°C)
Operating Temperature Range
Junction Temperature
727mW
-40°C to +85°C
+150°C
Storage Temperature Range
-65°C to +150°C
+300°C
Lead Temperature (soldering, 10s)
Note 1: Thermal properties are specified with product mounted on PC board with one square-inch of
copper area and still air.
Test Circuit
D1
L1
V
IN
V
OUT
+
2.5V to 10V
+
SS14
C3
C1
SS6896
C5
m
1 F
R1
R2
10 F
m
10 F/16V
1
3
m
6
4
IN
LX
FB
SHDN
SHDN
SS
GND
5
2
C2
m
0.033 F
Rev.2.01 6/06/2003
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SS6896
Electrical Characteristics (V =V
=3V, FB=GND, SS=Open, T = -40°C to 85°C,
A
SHDN
IN
unless otherwise specified)
PARAMETER
SYMBOL
MIN
TYP
MAX UNITS
CONDITIONS
Input Supply Range
V
2.5
10
30
V
V
V
IN
Output Voltage Adjust Range
V
OUT
V
Undervoltage Lockout
UVLO
V
V
V
rising, 50mV hysteresis
= 1.3V, not switching
= 1.0V, switching
2.2
0.1
1
IN
IN
0.2
5
FB
FB
Quiescent Current
I
mA
IN
V SHDN= 0, T = +25°C
0.01
0.01
0.5
10
µA
µA
A
Shutdown Supply Current
V SHDN = 0
ERROR AMPLIFIER
Feedback Regulation Set Point
FB Input Bias Current
Line Regulation
V
1.205 1.23 1.255
V
FB
I
FB
V
= 1.24V
FB
21
80
nA
2.6V < V < 5.5V
0.05
0.20
%/V
IN
OSCILLATOR
Frequency
f
1000 1400 1800 KHz
OSC
Maximum Duty Cycle
POWER SWITCH
Steady State Output Current
On-Resistance
DC
82
86
%
Io
Refer to Fig. 18
A
R
1
1.4
1
W
DS(ON)
V
V
= 12V, T = +25°C
0.1
LX
LX
A
Leakage Current
I
µA
LX(OFF)
= 12V
10
SOFT-START
Reset Switch Resistance
Charge Current
100
7.0
W
V
= 1.2V
1.5
1.0
4
µA
SS
CONTROL INPUT
Input Low Voltage
Input High Voltage
V
V SHDN, V = 2.5V to 10V
0.3
V
V
IL
IN
V
V SHDN, V = 2.5V to 10V
IN
IH
V SHDN = 3V
V SHDN = 0
25
50
SHDN Input Current
I SHDN
µA
0.01
0.1
Rev.2.01 6/06/2003
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SS6896
Typical Performance Characteristics
1.50
1.50
1.45
1.40
1.35
1.30
°
T =25 C
A
1.45
V =3.6V
IN
1.40
1.35
1.30
1.25
1.20
2
3
4
5
6
7
8
9
10
11
-40
-20
0
20
40
60
80
100
Supply Voltage (V)
Fig. 4 Frequency vs. Supply Voltage
°
Temperature ( C)
Fig. 3 Switching Frequency vs. Temperature
5.50
5.25
5.00
4.75
4.50
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
V =3.6V
IN
2
3
4
5
6
7
8
9
10
11
1
10
100
Output Current (mA)
Supply Voltage (V)
vs. Supply Voltage
Fig. 6 Load Regulation (L1=10
uH)
Fig. 5
R
DSON
12.5
12.0
11.5
11.0
10.5
2.4
2.2
2.0
1.8
1.6
V
IN
=3.6V
FB=1.0V
SHDN=1.0V
1.4
1.2
1.0
0.8
0.6
1
10
100
2
3
4
5
6
7
8
9
10
11
Output Current (mA)
Fig. 7 Load Regulation (L1=22uH)
Supply Voltage (V)
Fig. 8 Switching Current
Rev.2.01 6/06/2003
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SS6896
Typical Performance Characteristics (Continued)
90
90
V
=4.2V
IN
85
V =3.6V
IN
85
V
IN
=2.7V
V
IN
=3.3V
80
FB=1.3V
V
=2.5V
IN
80
SHDN=1.0V
75
75
70
70
65
V =5.0V
OUT
60
65
2
3
4
5
6
7
8
9
10
11
0
100
200
300
400
500
600
Supply Voltage (V)
Fig. 9 Non-Switching Current
Output Current (mA)
Fig. 10 Efficiency vs. Output Current (L1=10 H)
m
90
85
80
75
70
65
60
V
=12V
OUT
V
V
LX
V
=4.2V
IN
V =5.0V
IN
V
IN
=3.6V
OUT
V
=3.3V
IN
I
LX
0
50
100
150
200
Output Current (mA)
Fig. 11 Efficiency vs. output current (L1=22 H)
Fig. 12 Operation Wave Form
m
m
=5V;L1=10 H;R1=36K;R2=12K;
(V =3V;V
IN
OUT
C3=39pF;I
=200mA)
OUT
Rev.2.01 6/06/2003
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5 of 12
SS6896
Typical Performance Characteristics (Continued)
SHDN
V
SW
V
OUT
V
OUT
I
LX
I
LX
Fig. 13 Operation Wave Form
Fig. 14 Start-Up from Shutdown
m
=12V, L1=22 H; R1=105K;
(V =5V; V
IN
OUT
W
=300 )
(V =3.3V ;V
IN
=13V ;R
OUT
LOAD
R2=12K;C3=1nF;I
=200mA)
OUT
V
OUT
V
OUT
I
LX
I
LX
Fig. 16 Load Step Response
=12V ;L1=22uH; I =5mA to 150mA)
Fig. 15 Load Step Response
=5V;L1=10uH; I =5mA to 200mA)
(V =5V ; V
IN
OUT
OUT
(V =3.3V; V
IN
OUT
OUT
Rev.2.01 6/06/2003
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6 of 12
SS6896
Typical Performance Characteristics (Continued)
1.25
1.24
1.23
1.22
1.21
1.20
800
700
600
500
400
300
200
100
V
=13V
OUT
V
=9V
OUT
V
OUT
=5V
V
OUT
=15V
V
=3.6V
75
IN
-50
-25
0
25
50
100
2
3
4
5
6
7
8
9
10
°
Temperature ( C)
Supply Voltage (V)
Fig. 17 Feedback Pin Voltage
Fig. 18 Maximum Output current vs. Supply Voltage
m
m
(L1:10 H Vo=5V,9V ; L1=22 H Vo=13V,15V)
Block Diagram
VIN
PWM/PFM
C ontrol
I9
Soft- Start
SS
R4
R3
m
4 A
P W M
Error Amp
Comparator
C ontrol
Logic
SHDN
-
Driver
+
+
-
Q1
Q2
F B
RC
CC
1
8
R1
1.4MHz
Oscillator
LX
Slope
Compensation
x1
x20
R2
Current Amp x 5
+
-
RS
GND
Rev.2.01 6/06/2003
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SS6896
Pin Descriptions
SHDN with a slew rate of 0.1V/µs
PIN 1: LX
-
Power Switching Connection.
or
SHDN
draws up to 50µA.
Soft-Start Input.
greater.
Do
not
leave
Connect LX to inductor and output
unconnected.
SHDN
rectifier.
Keep
the
distance
between the components as close
to LX as possible.
PIN 5: SS
-
-
Connect
a
soft-start capacitor from SS to
GND in order to soft-start the
converter. Leave SS open to
disable the soft-start function.
PIN 2: GND - Ground.
PIN 3: FB Feedback Input. Connect
-
a
resistive voltage-divider from the
output to FB to set the output
voltage.
PIN 6: IN
Internal Bias Voltage Input.
Connect IN to the input voltage
source. Bypass IN to GND with a
capacitor sitting as close to IN as
possible.
PIN 4: SHDN - Shutdown Input. Drive SHDN
low to turn off the converter. To
automatically start the converter,
connect SHDN to IN. Drive
Rev.2.01 6/06/2003
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SS6896
Application Information
Inductor Selection
R1 = 1.23V/I
(1)
LED
A 15mH inductor is recommended for most SS6896
applications. Although small size and high efficiency
are major concerns, the inductor should have low
core losses at 1.4MHz and low DCR (copper wire
resistance).
Open-Circuit Protection
In the cases of output open-circuit, when the LEDs
are disconnected from the circuit or the LEDs fail,
the feedback voltage will be zero. The SS6896 will
then switch to a high duty cycle resulting in a high
output voltage, which may cause the SW pin
voltage to exceed its maximum 30V rating. A zener
diode can be used at the output to limit the voltage
on the SW pin (Fig. 20). The zener voltage should
be larger than the maximum forward voltage of the
LED string. The current rating of the zener should
be larger than 0.1mA.
Capacitor Selection
The small size of ceramic capacitors makes them
ideal for SS6896 applications. X5R and X7R types
are recommended because they retain their
capacitance over wider ranges of voltage and
temperature than other types, such as Y5V or Z5U.
A 4.7mF input capacitor and a 1mF output capacitor
are sufficient for most SS6896 applications.
Dimming Control
There are three different types of dimming control
Diode Selection
Schottky diodes, with their low forward voltage drop
and fast reverse recovery, are the ideal choices for
SS6896 applications. The forward voltage drop of a
Schottky diode represents the conduction losses in
the diode, while the diode capacitance (CT or CD)
represents the switching losses. For diode selection,
both forward voltage drop and diode capacitance
need to be considered. Schottky diodes with higher
current ratings usually have lower forward voltage
drop and larger diode capacitance, which can cause
significant switching losses at the 1.4MHz switching
frequency of the SS6896. A Schottky diode rated at
100mA to 200mA is sufficient for most SS6896
applications.
circuits as follows:
1. Using a PWM signal
PWM brightness control provides the widest
dimming range by pulsing the LEDs on and off using
the control signal. The LEDs operate at either zero
or full current, The average LED current changes
with the duty cycle of the PWM signal. Typically, a
1kHz to 10kHz PWM signal is used. PWM dimming
with the SS6896 can be accomplished two different
ways (see Fig. 21). The SHDN pin can be driven
directly or a resistor can be added to drive the FB
pin. If the SHDN pin is used, increasing the duty
cycle will increase the LED brightness. If the FB pin
is used, increasing the duty cycle will decrease the
brightness. Using this method, the LEDs are dimmed
using FB and turned off completely usingSHDN .
LED Current Control
LED current is controlled by a feedback resistor (R1
in Fig. 1). The feedback reference is 1.23V. The
LED current is 1.23V/R1. In order to have accurate
LED current, precision resistors are preferred (1%
recommended). The formula for R1 selection is
shown below.
2. Using a DC Voltage
For some applications, the preferred method of
brightness control uses a variable DC voltage to
adjust the LED current. The dimming control using a
Rev.2.01 6/06/2003
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SS6896
DC voltage is shown in Fig. 22. As the DC voltage
increases, the voltage drop on R2 increases and the
voltage drop on R1 decreases.
3. Using a Filtered PWM Signal
The filtered PWM signal can be considered as an
adjustable DC voltage. It can be used to replace the
variable DC voltage source in dimming control. The
circuit is shown in Fig. 23.
Thus, the LED current decreases. The selection of
R2 and R3 should make the current from the
variable DC source much smaller than the LED
current and much larger than the FB pin bias current.
For VDC range from 0V to 5V, the selection of
resistors in Fig. 22 gives dimming control of LED
current from 20mA to 0mA.
L1
D1
V
IN
m
10 H
3V to 4.2V
CH521S-30
C3
C1
4.7 F
ZD1
BZV55-B20
19.6V~20.4V
m
m
1 F
SS6896
6
4
1
3
IN
LX
FB
SHDN
OFF ON
R2
I
=I =20mA
OUT LED
SS
GND
1K
£ [
5
2
R1
62
£ [
C2
m
0.033 F
Fig. 20 White LED driver with open-circuit protection
ZD1
R2
ZD1
SS6896
SS6896
IN
LX
FB
IN
LX
R2
1K
PWM
SHDN
SS
SHDN
SS
FB
OFF
1KW
£
ON
GND
R1
GND
R1
62
R3
3.3KW
82W
£ [
C2
0.033mF
C2
0.033mF
PWM
(a)
(b)
Fig. 21 Dimming-control using a PWM signal
Rev.2.01 6/06/2003
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10 of 12
SS6896
ZD1
R2
SS6896
ZD1
R2
SS6896
IN
LX
FB
IN
LX
SHDN
SS
1K
OFF ON
£
SHDN
SS
FB
GND
R1
82
1K
OFF ON
£ [
20mA~0mA
R3
3.3K
£ [
GND
R1
82
£ [
R3
3.3K
C2
£ [
£ [
m
0.033 F
C2
4K
R4
C1
£ [
m
0.033 F
PWM
0V~5V
m
0.1 F
VDC
Fig. 22 Dimming-control using a DC voltage
Fig. 23 Dimming-control using a filtered PWM signal
Application Example
L1
D1
V
IN
m
10 H
3V to 4.2V
C1
CH521S-30
C3
m
4.7 F
m
1 F
ZD1
BZV55-B24
23.5V~24.5V
SS6896
1
3
6
4
LX
FB
IN
SHDN
OFF ON
GND
SS
R2
1K
5
2
£ [
I
=I
=20mA
OUT LED
C2
R1
62
R3
62
m
0.033 F
£ [
£ [
Fig. 24 Li-Ion powered driver for eight white LEDs with open-circuit protection
Rev.2.01 6/06/2003
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11 of 12
SS6896
Physical Dimensions
l SOT-23-6 (unit: mm)
SYMBOL
MIN
1.00
—
MAX
1.30
0.10
0.90
0.50
0.25
3.10
2.00
C
D
A
A1
A2
b
L
H
E
0.70
0.35
0.10
2.70
1.60
C
q
e
1
D
E
A
A2
e
1.90 (TYP)
A1
H
2.60
0.37
3.00
—
b
L
q1
1°
9°
Information furnished by Silicon Standard Corporation is believed to be accurate and reliable. However, Silicon Standard Corporation makes no
guarantee or warranty, express or implied, as to the reliability, accuracy, timeliness or completeness of such information and assumes no
responsibility for its use, or for infringement of any patent or other intellectual property rights of third parties that may result from its
use. Silicon Standard reserves the right to make changes as it deems necessary to any products described herein for any reason, including
without limitation enhancement in reliability, functionality or design. No license is granted, whether expressly or by implication, in relation to
the use of any products described herein or to the use of any information provided herein, under any patent or other intellectual property rights of
Silicon Standard Corporation or any third parties.
Rev.2.01 6/06/2003
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