5121X [GMT]
Fixed Frequency White LED Step-Up Converter; 固定频率白光LED升压转换器
| 型号： | 5121X |
| 厂家： | 
GLOBAL MIXED-MODE TECHNOLOGY INC |
| 描述： | Fixed Frequency White LED Step-Up Converter |
| 文件： | 总9页 (文件大小：579K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Global Mixed-mode Technology Inc.
G5121
Fixed Frequency White LED Step-Up Converter
Features
General Description
The G5121 is a step-up DC/DC converter specifically
designed to drive up to 5 series white LEDs with con-
stant current. Series connection of the LEDs provides
identical LED currents resulting in uniform brightness
and eliminates the need for ballast resistors. The
G5121 switches at 1MHz, allowing the use of tiny ex-
ternal components. A low 0.254V feedback voltage
minimizes power loss in the current setting resistor for
high efficiency. The OVP pin monitors the output volt-
age and turns off the converter whenever the LEDs
are open.
Inherently Matched LED Current
High Efficiency: 87%
Drives Up to Five LEDs from 2.5V Supply
24V Internal Power Switch
Fast 1MHz Switching Frequency
Uses Tiny 1mm Tall Inductors
Requires Only 1µF Output Capacitors
19.5V Over Voltage Protection
SOT-23-6 Package
Applications
The G5121 is available in low profile SOT-23-6 pack-
age.
White LED Backlight Display for PDA
Pocket PC
Smart Phones
Handheld Devices
Cellular Phones
Ordering Information
ORDER
NUMBER
TEMP.
RANGE
PACKAGE
(Pb free)
MARKING
G5121TB1U
5121x
-40°C ~ +85°C
SOT-23-6
Note: TB : SOT23-6
U: Tape & Reel
Pin Configuration
Typical Application Circuit
D1
L1
VIN
2.7V to 4.2V
4.7µH
1
6
5
4
VCC
OVP
SW
C2
1µF/25V
5 LEDs
VCC
SW
OVP
C1
4.7µF/6.3V
G5121
2
3
GND
FB
G5121
FB
SHDN
PWM Dimming
Waveform
GND
RS
SHDN
SOT-23-6
C1:TAIYO YUDEN, JMK212BJ475KD
C2:TAIYO YUDEN, TMK316BJ105KD
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
1
Global Mixed-mode Technology Inc.
G5121
Absolute Maximum Ratings
Junction Temperature......................….................125°C
Storage Temperature……....……..….….-65°C to 150°C
Reflow Temperature (soldering, 10sec)……...…260°C
ESD Rating (Human Body Model)………….….……2kV
VCC, SHDN to GND.….....................……-0.3V to +7V
FB to GND.....................….........................-0.3V to VCC
SW, OVP to GND……….……..…………..-0.3V to +24V
Operating Temperature.….…………….....-40°C to 85°C
Stress beyond those listed under “Absolute Maximum Rating” may cause permanent damage to the device.
Electrical Characteristics
(VCC=V SHDN =3.6V, TA=25°C)
PARAMETER
Input Voltage Range
CONDITIONS
MIN
2.5
1.7
18.5
13.5
---
TYP
---
MAX
6
UNITS
V
Input Voltage UVLO
2.0
19.5
15
2.3
21
V
Over Voltage Protection Threshold
Over Voltage Protection Threshold
OVP Pin Input Current
trigger
V
release
Vovp = 16V
16.5
60
V
40
µA
µA
mA
µA
mV
ppm/°C
MHz
%
VFB = 0.3V (no switching)
VFB = 0.2V (switching)
---
80
120
2
Quiescent Current
---
---
V
SHDN = 0V
---
0.1
254
100
1.0
---
1
Initial Accuracy
Temperature Coefficient
VFB = 0.2V
244
---
264
---
FB Comparator Trip Point
Switching Frequency
Maximum Duty
0.8
85
1.2
---
Switch RDS(ON)
ISW = 150mA
VSW = 20V
---
0.7
0.1
600
120
---
1.0
10
Ω
Switch Leakage Current
Switch Current Limit
Soft Start Time
---
µA
mA
µs
500
---
700
---
SHDN Pin Voltage High
SHDN Pin Voltage Low
2
---
V
---
---
0.8
V
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
2
Global Mixed-mode Technology Inc.
G5121
Typical Performance Characteristics
(VCC= +3.6V, V SHDN = +3.6V, L=4.7µH, TA=25°C, unless otherwise noted.)
Stability for Driving 4 WLEDs
Stability for Driving 5 WLEDs
Stability for Driving 2 WLEDs
Stability for Driving 3 WLEDs
Inrush Current for Driving 4 WLEDs
Inrush Current for Driving 5 WLEDs
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
3
Global Mixed-mode Technology Inc.
G5121
Typical Performance Characteristics (continued)
Inrush Current for Driving 2 WLEDs
Inrush Current for Driving 3 WLEDs
Dimming Control for Driving 4 WLEDs
OVP Waveform
Efficiency vs. Load Current
Efficiency vs. Load Current
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
VIN=2.7V
VIN=4.2V
VIN=2.7V
VIN=4.2V
VIN=3.6V
VIN=3.6V
5LEDs, CO=1µF
4LEDs, CO=1µF
20
0
5
10
15
20
25
0
5
10
15
25
Load Current (mA)
Load Current (mA)
TEL: 886-3-5788833
Ver: 1.1
http://www.gmt.com.tw
Nov 17, 2005
4
Global Mixed-mode Technology Inc.
G5121
Typical Performance Characteristics (continued)
Efficiency vs. Load Current
Efficiency vs. Load Current
90
80
70
60
50
40
30
20
10
90
80
70
60
50
40
30
20
10
VIN=2.7V
VIN=4.2V
VIN=3.6V
VIN=2.7V
VIN=3.6V VIN=4.2V
3LEDs, CO=1µF
2LEDs, CO=1µF
20
0
5
10
15
20
25
0
5
10
15
25
Load Current (mA)
Load Current (mA)
IQ_NoSW vs. Input Voltage
IQ_NoSW vs. Temperature
130
120
110
100
90
100
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
2
2.5
3
3.5
4
4.5
5
5.5
6
-40
-20
0
20
40
60
80
100
Input Voltage (V)
Temperature (°C)
Frequency vs. Input Voltage
Frequency vs. Temperature
1
0.95
0.9
1.1
1.05
1
0.95
0.9
0.85
0.8
0.85
0.8
0.75
0.7
0.75
0.7
-40
-20
0
20
40
60
80
100
2
2.5
3
3.5
4
4.5
5
5.5
6
Input Voltage (V)
Temperature (°C)
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
5
Global Mixed-mode Technology Inc.
G5121
Typical Performance Characteristics (continued)
OVP Trigger Threshold vs. Temperature
OVP Trigger Threshold vs. Input Voltage
21
20.5
20
21
20.5
20
19.5
19
19.5
19
18.5
18
18.5
18
17.5
17
17.5
17
-40
-20
0
20
40
60
80
100
2
2.5
3
3.5
4
4.5
5
5.5
6
Input Voltage (V)
Temperature (°C)
OVP Release Threshold vs. Input Voltage
OVP Release Threshold vs. Temperature
17
16.5
16
17
16.5
16
15.5
15
15.5
15
14.5
14
14.5
14
13.5
13
13.5
13
2
2.5
3
3.5
4
4.5
5
5.5
6
-40
-20
0
20
40
60
80
100
Input Voltage (V)
Temperature (°C)
OVP Pin Input Current vs. Input Voltage
OVP Pin Input Current vs. Temperature
60
50
40
30
20
10
0
60
50
40
30
20
10
0
2
2.5
3
3.5
4
4.5
5
5.5
6
-40
-20
0
20
40
60
80
100
Input Voltage (V)
Temperature (°C)
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
6
Global Mixed-mode Technology Inc.
G5121
Recommended Minimum Footprint
SOT-23-6
Block Diagram
FB
SW
OVP
COMPENSATION
COMPARATOR
DRIVER
A1
CONTROL
+
A2
R
Q
M1
S
+
0.254V
VREF
RAMP
GENERATOR
+
OC
1MHz
OSCILLATOR
VCC
GND
SHDN
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
7
Global Mixed-mode Technology Inc.
G5121
Pin Description
PIN
1
NAME
SW
FUNCTION
Switch Pin. The drain of the internal NMOS power switch. Connect this pin to inductor.
2
GND
Ground Pin.
Feedback Pin. Connect current setting resistor Rs from this pin to ground. The LED current is set as
3
4
FB
0.254V/ Rs.
Active Low Shutdown Pin.
SHDN
OVP
VCC
5
6
Over Voltage Protection Sense Pin.
Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible.
Function Description
Since the G5121 is designed to operate in discontinu-
ous mode, the inductor current reaches zero during
discharge phase. After the inductor current reaches
zero, the switch pin exhibits ringing due to the LC tank
circuit formed by the inductor in combination with
switch and diode capacitance. This ringing is not
harmful; far less spectral energy is contained in the
ringing than in the switch transitions. The ringing can
be damped by application of a 300Ω resistor across
the inductor, although this will degrade efficiency.
Normal Operation
The G5121 uses a constant frequency control scheme
to provide excellent line and load regulation. Operation
can be best understood by referring to the block dia-
gram. At the start of each oscillator cycle, the SR latch
is set, which turns on the power switch M1. An artificial
ramp is generated to the positive terminal of the PWM
comparator A2. When this voltage exceeds the level at
the negative input of A2, the SR latch is reset turning
off the power switch. The level at the negative input of
A2 is set by the error amplifier A1, and is simply an
amplified version of the difference between the feed-
back voltage and the reference voltage of 0.254V. In
this manner, the error amplifier sets the correct peak
current level to keep the output in regulation. If the
error amplifier’s output increases, more current is de-
livered to the output, if it decreases, less current is
delivered.
Capacitor Selection
The small size of ceramic capacitors makes them suit-
able for G5121 applications. X5R and X7R types are
recommended because they retain their capacitance
over wider voltage and temperature ranges than other
types such as Y5V or Z5U. A minimum 1µF capacitor
for output is required for most applications. Larger in-
put/output capacitor minimizes input/output ripple.
Diode Selection
Over Voltage Protection
Schottky diodes, with their low forward voltage drop
and fast reverse recovery, are the ideal choices for
G5121 applications. The forward voltage drop of a
Schottky diode represents the conduction losses in the
diode, while the diode capacitance (CT or CD) repre-
sents 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 1MHz switching frequency of
the G5121. A Schottky diode rated at 500mA is suffi-
cient for most G5121 applications.
Over voltage protection function is designed to prevent
the damage of internal NMOS switch in case the in-
creased impedance of the LED load (include the LED
opened). Once the device detects over voltage (typical
19.5V) at the output, the internal NMOS switch is kept
off until the output voltage drops below 15V.
Application Information
Inductor Selection
A 4.7µF inductor is recommended for G5121 applica-
tions. Small size and high efficiency are the major
concerns for most G5121 applications. Inductor with
low core losses and small DCR (cooper wire resis-
tance) at 1MHz are good choice for G5121 applica-
tions.
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
8
Global Mixed-mode Technology Inc.
G5121
Package Information
C
D
L
H
E
θ1
e1
e
A
A2
A1
b
Note:
1. Package body sizes exclude mold flash protrusions or gate burrs
2. Tolerance ±0.1000 mm (4mil) unless otherwise specified
3. Coplanarity: 0.1000mm
4. Dimension L is measured in gage plane
DIMENSION IN MM
SYMBOL
DIMENSION IN INCH
MIN.
1.00
0.00
0.70
0.35
0.10
2.70
1.40
-----
NOM.
1.10
MAX.
1.30
0.10
0.90
0.50
0.25
3.10
1.80
-----
MIN.
0.039
0.000
0.028
0.014
0.004
0.106
0.055
-----
NOM.
0.043
-----
MAX.
0.051
0.004
0.035
0.020
0.010
0.122
0.071
-----
A
A1
A2
b
-----
0.80
0.031
0.016
0.006
0.114
0.063
0.075(TYP)
0.110
-----
0.40
C
0.15
D
2.90
E
1.60
e
1.90(TYP)
2.80
H
2.60
0.37
1º
3.00
-----
0.102
0.015
1º
0.118
-----
L
------
θ1
5º
9º
5º
9º
Taping Specification
PACKAGE
Q’TY/REEL
3,000 ea
SOT-23-6
Feed Direction
SOT- 23-6 Package Orientation
GMT Inc. does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and GMT Inc. reserves the right at any time without notice to change said circuitry and specifications.
TEL: 886-3-5788833
http://www.gmt.com.tw
Ver: 1.1
Nov 17, 2005
9
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