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AME, Inc.
AME5138
n General Description
The AME5138 is a fixed off-time step-up DC/DC converter in a small 5-lead SOT-25 package.The AME5138 is ideal for LCD panels requiring low current and high efficiency as well as LED applications for cellular phone backlighting, PDAs,and other hand-held devices. The low 400ns off-time allows the use of tiny external components. AME5138 is designed to drive up to four white LEDs in series with a constant current from a single Li-lon battery. To control LED brightness, the LED current can be adjusted by applying a PWM (pulse width modulated) signal with a frequency range of 100Hz to 50KHz to the EN pin.
Micropower Step-Up DC/DC Converter
n Typical Application
V IN 2.5V-4.2V 5 V IN L 10H 1 SW ILED COUT 1F Ceramic D Option for 4LEDs
CIN 4.7F Ceramic
AME5138
>1.1V 4 EN 0V GND 2 FB
3 R2 80
* ILED =VFB/R2
n Features
l 0.7 internal switch l Uses small surface mount components l Adjustable output voltage up to 20V l 2V to 5.5V input range l Input undervoltage lockout l 0.01A shutdown current l Small 5-Lead SOT-25 package l All AME's lead free Product Meet RoHS Standard
Figure 1G Four White LEDs Application in Li-lon Battery
VIN 2.5V-4.2V
L 15H
D
20V 10mA
5 CIN 4.7F Ceramic 4 VIN
1 SW 3
R1 200K
AME5138 FB EN GND 2
COUT 1F Ceramic
R2 13K
n Applications
l l l l l White LED Back-Lighting Hand-held Devices Digital Cameras Portable Applications LCD Bias Power Figure 2G Typical 20V Application
1
AME, Inc.
AME5138
n Function Block Diagram
L VIN CIN VIN SW D
Micropower Step-Up DC/DC Converter
VOUT
COUT
VOUT Vref=1.23 Enable Comp
R1
FB
+
R2 400ns one Shot
+ CL Comp Current sensing
CL Adjust Driver Under Voltage Lockout Logic control
EN
GND
Figure 3G AME5138 Block Diagram
2
AME, Inc.
AME5138
n Pin Configuration
SOT-25 Top View
5 4
Micropower Step-Up DC/DC Converter
AME5138 1. SW 2. GND
AME5138
3. FB 4. EN 5. VIN
1
2
3
* Die Attach: Conductive Epoxy
n Pin Description
Pin Number
1
Pin Name
SW
Pin Description
Power Switch input. This is the drain of the internal NMOS power switch. Minimize the metal trace area connected to this pin to minimize EMI. Ground. Tie directly to ground plane. Output voltage feedback input. Set the output voltage by selecting values for R1 and R2 using:
2
GND
3
FB
V R1 = R 2 out - 1 1 . 23V
Connect the ground of the feedback network to an AGND(Analog Ground) plane which should be tied directly to the GND pin.
4
EN
Shutdown control input, active low. The shutdown pin is an active low control. Tie this pin above 1V to enable the device. Tie this pin below 0.4V to turn off the device. Analog and Power input. Input Supply Pin. Bypassed this pin with a capacitor as close to the device as possible.
5
VIN
3
AME, Inc.
AME5138
n Ordering Information AME5138 x x x x xxx x
Special Feature Output Voltage Number of Pins Package Type Operating Ambient Temperature Range Pin Configuration
Micropower Step-Up DC/DC Converter
Pin Configuration A
(SOT-25)
Operating Ambient Package Type Temperature Range E: -40OC to +85OC E: SOT-2X
Number of Pins V: 5
Output Voltage
Special Feature
1. SW 2. GND 3. FB 4. EN 5. VIN
ADJ: Adjustable
Y: Lead free & Low profile Z: Lead free
n Ordering Information
Part Number
AME5138AEEVADJY AME5138AEEVADJZ
Marking*
BDYww BDYww
Output Voltage
ADJ ADJ
Package
TSOT-25 SOT-25
Operating Ambient Temperature Range
-40OC to +85OC -40OC to +85OC
Note: ww represents the date code and pls refer to Date Code Rule before Package Dimension. * A line on top of the first letter represents lead free plating such as BDYww. Please consult AME sales office or authorized Rep./Distributor for the availability of package type.
4
AME, Inc.
AME5138
n Absolute Maximum Ratings
Parameter
Input Supply Voltage EN, VFB Voltages SW Voltage N-Channel Switch Sink Current ESD Classification
Micropower Step-Up DC/DC Converter
Symbol
VIN VEN ,VFB VSW ISW
Maximum
6 VIN VOUT+0.3 800 B*
Unit
V V V mA
Caution: Stress above the listed absolute maximum rating may cause permanent damage to the device * HBM B:2000V~3999V
n Recommended Operating Conditions
Parameter
Input Supply Voltage Ambient Temperature Range Junction Temperature Range
Symbol
VIN TA TJ
Rating
2 to 5.5 -40 to +85
Unit
V
o
C
-40 to +125
n Thermal Information
Parameter
Thermal Resistance* (Junction to Case) Thermal Resistance (Junction to Ambient) Internal Power Dissipation Maximum Junction Temperature Solder Iron (10 Sec)** * Measure JC on backside center of molding compund if IC has no tab. ** MIL-STD-202G210F
5
Package
Die Attach
Symbol
JC
Maximum
81
Unit
o
C/W
SOT-25
Conductive Epoxy
JA
PD
260
400 150 350
mW
o
C C
o
AME, Inc.
AME5138
n Electrical Specifications
VIN=2.2V, EN = VIN, TA= 25oC Unless otherwise noted. Parameter Input Voltage Range Symbol VIN
o
Micropower Step-Up DC/DC Converter
Test Condition TA=-40 C to +85 C FB = 1.3V (Not Switching) TA=25oC VIN =5.5V TA= -40 to 85oC TA=25oC VIN =5.5V TA= -40 to 85oC
o
Min 2
Typ
Max 5.5
Units V
64
80 150
Quiescent Crrrent
IQ FB = 1.15V (Switching)
69
90 150
A
Shutdown Current Feedback Trip Point Feedback Hysteresis FB Pin Bias Current Switch Current Limit Switch RDSON Switch Off Time Switch Leakage Current Input Undervoltage Lockout EN Input Threshold (Low) (Shutdown) EN Input Threshold (High) (Enable the device)
ISC VFB VFB Hysteresis IFB ICL RDSON tOFF ISW UVP
EN = 0V TA=-40oC to +85oC TA= 25oC FB = 1.23V IOUT=10mA VOUT=20V TA= -40 to 85oC TA= -40 to 85oC TA=25oC TA= -40 to 85oC 325 300 1.199
0.01 1.23 8 0.2 350
2 1.261 V mV 0.7 375 mA 400 A
0.7 400
1.6
ns
VSW = 20V ON/OFF Threshold TA= -40 to 85oC
0.05 1.6
5.0
V
0.4 V
EN Threshold
TA= -40 to 85 C EN = VIN , TA = 25oC
o
1 0 15 0 nA
EN input Current
IEN
EN = VIN , TA = 85oC EN = GND
6
AME, Inc.
AME5138
n Detailed Description
The AME5138 features a constant off-time control scheme. Operation can be best understood by referring to Figure 3. When the voltage at the FB pin is less than 1.23V, the Enable Comp in Figure 3 enables the device and the NMOS switch is turmed on pulling the SW pin to ground. When the NMOS switch is on, current is supplied by the output capacitor COUT. Once the current in the inductor reaches the peak current limit, the 400ns One Shot turns off the NMOS switch. The SW voltage will then rise to the output voltage plus a diode drop and the inductor current will begin to decrease as shown in Figure 3. During this time the energy stored in the inductor is transferred to COUT and the load. After the 400ns off-time the NMOS switch is turned on and energy is stored in the inductor again. This energy transfer from the inductor to the output causes a stepping effect in the output ripple. This cycle is continued until the voltage at FB reaches 1.23V. When FB reaches this voltage, the enable comparator then disables the device turning off the NMOS switch and reducing the Iq of the device to 64A. The load current is then supplied solely by COUT indicated by the gradually decreasing slope at the output. When the FB pin drops slightly below 1.23V, the enable comparator enables the device and begins the cycle described previously. The EN pin can be used to turn off the AME5138 and reduce the Iq to 0.01A. In shutdown mode the output voltage will be a diode drop lower than the input voltage.
Micropower Step-Up DC/DC Converter
n Application Information
INDUCTOR SELECTION The appropriate inductor for a given application is calculated using the following equation:
V - VIN(min) + VD TOFF L = OUT ICL
Where V D is the schottky diode voltage, ICL is the switch current limit found in the Typical Performance Characteristics section, and TOFF is the switch off time. When using this equation be sure to use in minimum input voltage for the application, such as for battery powered applications. Choosing inductors with low ESR decrease power lossed and increase efficiency. Care should be taken when choosing an inductor. For applications that require an input voltage that approaches the output voltage, such as when converting a Li-ion battery voltage to 5V, the 400ns off time may not be enough time to discharge the energy in the inductor and transfer the energy to the output capacitor and load. This can cause a ramping effect in the inductor current waveform and an increased ripple on the output voltage. Using a smaller inductor will cause the IPK to increase and will increase the output voltage ripple further. This can be solved by adding a 4.7pF capacitor across the R1 feedback resistor (Figure 3) and slightly increasing the output capacitor. A smaller inductor can then be used to ensure proper discharge in the 400ns off time. DIODE SELECTION To maintain high efficiency, the average current rating of the schottky diode should be larger than the peak inductor current, IPK. Schottky diodes with a low forward drop and fast switching speeds are ideal for increasing efficiency in portable applications. Choose a reverse breakdown of the schottky diode larger than the output voltage.
7
AME, Inc.
AME5138
CAPACITOR SELECTION Choose low ESR capacitors for the output to minimize output voltage ripple. Multilayer ceramic capacitors are the best choice. For most applications, a 1F ceramic capacitor is sufficient. For some applications a reduction in output voltage ripple can be achieved by increasing the output capacitor. Local bypassing for the input is needed on the AME5138. Multilayer ceramic capacitors are a good choice for this as well. A 4.7F capacitor is sufficient for most applications. For additional bypassing, a 100nF ceramic capacitor can be used to shunt high frequency ripple on the input.
Micropower Step-Up DC/DC Converter
LAYOUT CONSIDERATIONS The input bypass capacitor CIN, as shown in Figure 3, must be placed close to the IC. This will reduce copper trace resistance which effects input voltage ripple of the IC. For additional input voltage filtering, a 100nF bypass capacitor can be placed in parallel with CIN to shunt any high frequency noise to ground. The output capacitor, COUT, should also be placed close to the IC. Any copper trace connections for the COUT capacitor can increase the series resistance, which directly effects output voltage ripple. The feedback network, resistors R1 and R2, should be kept close to the FB pin to minimize copper trace connections that can inject noise into the system. The ground connection for the feedback resistor network should connect directly to an analog ground plane. The analog ground plane should tie directly to the GND pin. If no analog ground plane is available, the ground connection for the feedback network should tie directly to the GND pin. Trace connections made to the inductor and schottky diode should be minimized to reduce power dissipation and increase overall efficiency.
8
AME, Inc.
AME5138
n Application Information
VIN 2.5V-4.2V 5 C IN 4.7F Ceramic 4 VIN L 2.2H D
Micropower Step-Up DC/DC Converter
5V 60mA
1 SW 3
R1 100K
CF B 5pF
AME5138 FB EN GND 2
C OUT 1F Ceramic
R2 32.4K
Figure5: Li-Ion 5V Application
VIN 2.5V-4.5V 5 C IN 4.7F Ceramic 4 VIN
L 10H
D
12V 20mA
1 SW 3
R1 100K
AME5138 FB EN GND 2
C OUT 1F Ceramic
R2 11.3K
Figure6: Li-Ion 12V Application
VIN 5V 5 C IN 4.7F Ceramic 4 VIN
L 10H
D
12V 40mA
1 SW 3
R1 100K
AME5138 FB EN GND 2
C OUT 1F Ceramic
R2 11.3K
Figure7: 5V to 12V Application
9
AME, Inc.
AME5138
Switch Current Limit vs. VIN
450
Micropower Step-Up DC/DC Converter
Efficiency vs. Load Current
90 85 80 VIN =4.2V V IN =3.3V VIN =2.5V
Switch Current Limit (mA)
400
Efficiency (%)
75 70 65 60 55 50
o
TA =-40 C 350 TA =25 C 300 TA=85 C 250 2 2.5 3 3.5 4 4.5 5 5.5
o
o
45 40 35 0.5 2 6 10 13
VOUT =20V
14 17
VIN (V)
IOUT (mA)
Efficiency vs. Load Current
90 85 80 VIN =5V VIN =3.3V V IN =2.5V
Efficiency vs. Load Current
95 90 VIN =4.2V
V IN =4.2V
85
VI N=3.3V
VIN =2.5V
Efficiency (%)
75 70 65 60 55 50 45 40 0.5 2 6 10
Eff iciency (%)
V OUT =12V
80 75 70 65 60 55 50 45 40
VOUT=5V
6 18 34 65 85 110 130 150 190
14 18 22 24 25 26 30
31 37 38 46
0.5
IOUT (mA)
IOUT (mA)
Enable Current vs. VIN (Part Switching)
140 130
Disable Current vs. VIN (Part Not Switching)
140 130
110 100 90 80 70 60 50 40 2 2.5 3 3.5 4 4.5 5 5.5 6
o
Disab le Current (A)
Enable Current ( A)
120
120 110 100 90 80 70 60 50 40 2 2.5 3 3.5 4 4.5 5 5.5 6 TA =-40 C
o o
TA=85 C
o
TA=25 C
o
TA =85 C
o
TA =25 C
TA=-40 C
VI N (V)
VIN (V)
10
AME, Inc.
AME5138
EN Threshold vs. VIN
1.05 1.0 0.95
1.2 1.1 1
Micropower Step-Up DC/DC Converter
Switch Rdson vs. VIN
EN Threshold (V)
0.9 0.85 0.8 0.75 0.7 0.65 0.6 0.55 0.5 2 2.5 3 3.5 4 4.5 5 5.5 TA=85 C
o
TA =-40 C
o
Rd so n ( )
TA=25 C
o
0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 TA =-40 C
o o
TA=85 C
TA=25 C
o
6
2
2.5
3
3.5
4
4.5
5
5.5
6
VIN (V)
VIN (V)
Efficiency vs. VIN
90
12.2 12.15
Output Voltage vs Load Current
Outp ut Vo ltage (V)
85
12.1 12.05 12 11.95 11.9 11.85
VIN =2.5V
Efficien cy (%)
VIN =3.3V VIN =4.2V
T A=25 C
80
o
V IN =5V
75
4 LEDs IOUT=15mA
70 2 2.5 3 3.5 4 4.5 5
C OUT =4.7F VOUT =12V
6 10 14 18 22 24 26 30 32 33 38 40 42 52
11.8 0.5 2
VI N (V)
IOUT (mA)
FB Trip Point and FB Pin Current vs Temperature
1.25 0.36 0.35 1.24 V FB 1.23 0.34 0.33 0.32 0.31 1.21 IFB 0.3 1.2 -40 0.29 85
1.22
-20
0
25 o
55
Ambient Temperature ( C)
Feeback Biascurent (A)
Feeback Trip Point (V)
11
AME, Inc.
AME5138
Typical Switching Waveform
Micropower Step-Up DC/DC Converter
Typical Switching Waveform
1
1
3
2
2
3
VOUT=20V, VIN=2.5V 1)V SW, 20V/div,DC 2)V OUT, 200mV/div.AC 3)Inductor Current, 200mA/div,DC Load Current=10mA T=10ms/div Step Response
VOUT = 14V, VIN=3.6V; 4LEDs IOUT = 15mA 1) VSW, 20V / div, DC 2) Inductor Current, 100mA / div, DC 3) VOUT, 100mV / div. AC
Start-Up/Shutdown
1
1
2
2
3
3
VOUT=20V, VIN=2.5V 1)Load, 1mA to 10mA to 1mA,DC 2)V OUT, 200mV/div.AC 3)Inductor Current 200mA/div,DC T=1ms/div
VOUT = 20V, VIN = 2.5V 1) EN, 1V/div,DC 2) VOUT, 20V/div,DC 3) Inductor Current 200mA/div,DC RL =1.8k, T= 200s/div
12
AME, Inc.
AME5138
n Date Code Rule
Marking A A A A A A A A A A A A A A A A A A A A A A A A A A A A A A Date Code W W W W W W W W W W W W W W W W W W W W Year xxx0 xxx1 xxx2 xxx3 xxx4 xxx5 xxx6 xxx7 xxx8 xxx9
Micropower Step-Up DC/DC Converter
n Tape and Reel Dimension
SOT-25
P
W AME PIN 1 AME
Carrier Tape, Number of Components Per Reel and Reel Size Package SOT-25 Carrier Width (W) 8.00.1 mm Pitch (P) 4.00.1 mm Part Per Full Reel 3000pcs Reel Size 1801 mm
13
AME, Inc.
AME5138
n Tape and Reel Dimension
TSOT-25
P
Micropower Step-Up DC/DC Converter
W AME PIN 1 AME
Carrier Tape, Number of Components Per Reel and Reel Size Package TSOT-25 Carrier Width (W) 8.00.1 mm Pitch (P) 4.00.1 mm Part Per Full Reel 3000pcs Reel Size 1801 mm
14
AME, Inc.
AME5138
n Package Dimension
SOT-25
Top View D
L
Micropower Step-Up DC/DC Converter
Side View
SYMBOLS A A1
MILLIMETERS MIN MAX
INCHES MIN MAX
1.20REF 0.00 0.30 2.70 1.40 0.15 0.55 3.10 1.80
0.0472REF 0.0000 0.0118 0.1063 0.0551 0.0059 0.0217 0.1220 0.0709
E
b D E
S1 e c1
H
e H L 1
1.90 BSC 2.60 3.00
0.07480 BSC 0.10236 0.11811 0.0146BSC
o
0.37BSC 0
o
Front View
A
10
0o
10o
S1
0.95BSC
0.0374BSC
b
TSOT-25
Top View D
L
A1
Side View
SYMBOLS A+A1 b
MILLIMETERS MIN
0.90 0.30 0.09 2.70 1.40
INCHES MIN
0.0354 0.0118 0.0035 0.1063 0.0551
MAX
1.25 0.50 0.25 3.10 1.80
MAX
0.0492 0.0197 0.0098 0.1220 0.0709
H
E
c D E
S1 e c1
e H L 1 S1
1.90 BSC 2.40 3.00
0.07480 BSC 0.09449 0.11811 0.0138BSC
o
0.35BSC 0
o
Front View
A
10
0o
10o
0.95BSC
0.0374BSC
b
A1
15
www.ame.com.tw
E-Mail: sales@ame.com.tw
Life Support Policy: These products of AME, Inc. are not authorized for use as critical components in life-support devices or systems, without the express written approval of the president of AME, Inc. AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. (c) AME, Inc. , February 2006 Document: 1015-DS5138-A.01
Corporate Headquarter
AME, Inc.
2F, 302 Rui-Guang Road, Nei-Hu District Taipei 114, Taiwan. Tel: 886 2 2627-8687 Fax: 886 2 2659-2989
U.S.A. (Subsidiary)
Analog Microelectronics, Inc.
3100 De La Cruz Blvd., Suite 201 Santa Clara, CA. 95054-2046 Tel : (408) 988-2388 Fax: (408) 988-2489

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