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AMC3202
www.addmtek.com DESCRIPTION The AMC3202 is a 280kHz switching regulator with a high efficiency, 1.5A integrated switch. The part operates over a wide input voltage range, from 2.7V to 30V. The AMC3202 utilizes current mode architecture, which allows excellent load and line regulation, as well as a practical means for limiting current. Combining high frequency operation with a highly integrated regulator circuit results in an extremely compact power supply solution. Build-in thermal protection to prevent the chip over heat damage.
1.5A 280kHz BOOST REGULATORS
FEATURES Integrated Power Switch: 1.5A Guaranteed. Wide Input Range: 2.7V to 30V. 43V Build-in Power Switch Input Voltage. High Frequency Allows for Small Components. Minimum External Components. Built in Over Current Protection.
TYPICAL APPLICATION CIRCUIT
APPLICATIONS
2.7 ~ 30VDC
L
DF
VOUT
COUT
VIN
CIN Enable DSS
SS COMP AGND PGND VCC EN VSW
TFT-LCD Power Management LED Backlight
R2
FB
PACKAGE PIN OUT
AMC3202
R1
COMP FB SS EN
1 2 3 4
8 7 6 5
VSW PGND AGND VCC
CSS CP2
CP1 RP
SO-8 (Top View)
ORDER INFORMATION
DM
SO 8 pin AMC3202DMF (Lead Free)
Note:
All surface-mount packages are available in Tape & Reel. Append the letter "T" to part number (i.e. AMC3202DMFT). The letter "F" is marked for Lead Free process.
Copyright (c) 2006 ADDtek Corp.
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ABSOLUTE MAXIMUM RATINGS Input Voltage, VCC Switch Input Voltage, VSW Maximum Operating Junction Temperature, TJ Storage Temperature Range Lead Temperature (Soldering, 10 seconds)
Note: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal. (Note)
30V 43V 150C -65C to 150C 260C
BLOCK DIAGRAM
VCC
5
Shutdown Delay Timer 2.0V Regulator Thermal Shutdown
8 VSW
Sync Oscillator S PWM Latch R 0.4V Detector Frequency Shift 5:1 X5 Q Driver Switch
EN
4
4uA
SS
3
FB
2
1.276V
Error Amp
PWM Comparator Slope Compensation
63m
AGND
6 1
COMP
Ramp Summer
7
PGND
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PIN DESCRIPTION Pin Number 1 2 3 4 5 6 7 8 Exposed Pad Pin Name COMP FB SS EN VCC AGND PGND VSW Heat Pad (PGND) Pin Function Loop compensation pin. This pin is the output of the error amplifier and is used for loop compensation. Loop compensation can be implemented by a simple RC network. Feedback pin. Sense the output voltage and referenced to 1.276V. When the voltage at this pin falls below 0.4V, chip switching-frequency reduces to a much lower frequency. Soft Start pin. Left this pin floating if soft start function is not used. Enable pin. A TTL low will shut down the chip and high enable the chip. This pin may also be used to synchronize the part to nearly twice the base frequency. If synchronization is not used, this pin should be either tied high or left floating for normal operation. Input power supply pin. Supply power to the IC and should have a bypass capacitor connected to AGND. Analog ground. Provide a clean ground for the controller circuitry and should not be in the path of large currents. This pin is connected to the IC substrate. Power ground. This pin is the ground connection for the emitter of the power switching transistor. Connection to a good ground plane is essential. High current switch pin. Connect to the collector of the internal power switch. The open voltage across the power switch can be as high as 40V. To minimize radiation, use a trace as short as practical. Heat pad. Connect to power ground. Must be soldered to electrical ground on PCB.
THERMAL DATA Thermal Resistance from Junction to Ambient, JA
Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/pc-board system. Connect the ground pin to ground using a large pad or ground plane for better heat dissipation. All of the above assume no ambient airflow. Maximum Power Calculation: PD(MAX)= TJ (C): TA (C): JA ( C /W):
O
165C /W
TJ(MAX) - TA(MAX) JA Maximum recommended junction temperature Ambient temperature of the application Junction-to-Ambient thermal resistance of the package, and other heat dissipating materials.
The maximum power dissipation for a single-output regulator is: PD(MAX) = [(VIN(MAX) - VOUT(NOM))] x IOUT(NOM) + VIN(MAX) x IQ Where: VOUT(NOM) = the nominal output voltage IOUT(NOM) = the nominal output current, and IQ = the quiescent current the regulator consumes at IOUT(MAX) VIN(MAX) = the maximum input voltage Then JA = (+150 OC - TA)/PD
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RECOMMENDED OPERATING CONDITIONS Parameter Supply Voltage Average Supply Current Output Voltage Operating Free-air Temperature Range Symbol VIN IIN VOUT TA Min 2.7 Typ Max 30 1.3 42 85C Unit V A V C
DC ELECTRICAL CHARACTERISTICS VCC = 3.3V, TA = 25C, (Unless otherwise noted) Parameter FB Reference Voltage FB Input Current FB Reference Voltage Line Regulation Error Amp Transconductance Error Amp Gain COMP Source Current COMP Sink Current COMP High Clamp Voltage COMP Low Clamp Voltage COMP Threshold Base Operating Frequency Reduced Operating Frequency Maximum Duty Cycle FB Frequency Shift Threshold Synchronization Range Synchronization Pulse Transition Threshold EN Bias Current Shutdown Threshold Shutdown Delay 2.7VVCC12V 12VVCC30V Rise time=20ns EN=0V EN=3.0V Conditions COMP tied to FB; Measure at FB; 2.7VVCC30V FB=VREF COMP=FB, 2.7VVCC30V ICOMP=25uA (Note)
(Note)
Min 1.246 -1.0 300 200 25 200 1.5 0.25 0.75 230 30 90 0.36 320 2.5 -15 0.50 12 12
Typ 1.276 0.1 0.01 550 500 50 625 1.7 0.50 1.05 280 52 94 0.40 -3.0 3.0 0.85 80 36
Max 1.300 1.0 0.03 800 90 1500 1.9 0.65 1.30 310 120 0.44 500 8.0 1.20 350 200
Unit V uA %/V uMh o V/V uA uA V V V kHz kHz % V kHz V uA V uS
FB=1.0V, COMP=1.25V FB=1.5V, COMP=1.25V FB=1.0V, COMP sources 25uA FB=1.5V, COMP sinks 25uA Reduce COMP from 1.5V until switching stops FB=1V FB=0V FB=1V Frequency drops to reduced operating frequency
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ISWITCH=1.5A Switch Saturation Voltage ISWITCH=1.0A, 0CTJ85C (Note) ISWITCH=1.0A, -40CTJ0C (Note) ISWITCH=10mA Switch Current Limit Minimum Pulse Width Switch Leakage 50% duty cycle (Note) 80% duty cycle (Note) COMP=1.4V, ISW = 1.0A VSW=43V, VCC=0V 2.7VVCC12V, 10mAISW1.0A ICC/Isw 12VVCC30V, 10mAISW1.0A 2.7VVCC12V, 10mAISW1.5A 12VVCC30V, 10mAISW1.5A Operating Current Shutdown Mode Current Minimum Operation Input Voltage Thermal Shutdown Thermal Hysteresis
Note: Guaranteed by design, not 100% tested in production.
1.6 1.5 100 150 -
0.8 0.55 0.75 0.09 1.9 1.7 250 2.0 10 17 5.5 12 2.45 25
1.4 0.45 2.4 2.2 300 10 30 100 30 100 8.0 60 100 2.70 -
V
A nS uA
mA/A
ISW=0; 2.7VVCC30V COMP0.8V, EN=0V, 2.7VVCC12V COMP0.8V, EN=0V, 12VVCC30V VSW switching, maximum ISW=10mA
mA uA V C C
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CHARACTERIZATION CURVES
Switch Frequency vs. FB
25
300 250 Frequency(kHz) 200 150 100 50 0 0.36 0.38 0.4 FB(V) 0. 42 0. 44 VCC=3.3V TA=25C
Icc vs. VCC During Shutdowm
20
15 Icc(uA)
10 VCC=2.7V~30V TA=25C 0 0 10 VCC(V) 20 30
5
Reference Voltage vs. Temperature
1. 280 1. 278 1. 276 Voltage(V) 1. 274 1. 272 1. 270 1. 268 1. 266 1. 264 -40 0 40 Temperature(C) 80 120 I EN(uA) VCC=3.3V 1 0. 75 0.5 0. 25 0 -0. 25 -0.5 -0. 75 -1
IEN vs. VEN
VCC=3.3V TA=25C
0
3 VEN(V)
6
9
VCE (SAT) vs. ISW
0.7 0.6 0.5 VCE (SAT) (mV) 1 0.4 0.3 0.2 0.1 0 0 500 Isw(mA) 1000 1500 Voltage(V) 0. 9 0. 8 0. 7 0. 6 VCC=3.3V TA=25C 1. 2 1. 1
COMP Threshold vs. Temperature
VCC=3.3V TA=25C
-40
0
40 Temperature(C)
80
120
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Shutdown Delay vs. Temperature
160 140 120 Delay(ns) VCC=2.7V VCC=30V VCC=12V
Switching FOSC vs. Temperature
285 280 275
80 60 40 20 0 -40 0 40 Temperature(C) 80 120
Fosc(kHz)
100
270 265 260 255 250 245 -40 0 40 80 120
Temperature(C)
Minimum VCC vs. Temperature
1.85 1. 825 1. 8 VCC,MIN(V) 1. 775 1.75 1. 725 1. 7 -40 0 40 80 120
0.35 0. 3 0.25 Current(mA) 0. 2 0.15 0. 1 0.05 0
Switch Leakage vs. Temperature
VCC=0V TA=25C
-40
0
40 Temperature(C)
80
120
Temperature(C)
Max Duty Cycle vs. Temperature
99.5 VCC=30V 99.3 VCC=2.7V Duty Cycle(%) 99.1
98.9
VCC=12V
VCC=3.3V
98.7
VCC=2.7V ~30V TA=25C -40 0 40 Temperature(C) 80 120
98.5
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APPLICATION INFORMATION
Operation:
The AMC3202 incorporates a current mode control scheme, in which the duty cycle of the switch is directly controlled by switch current rather than by output voltage. The output of the oscillator turns on the power switch at a frequency of 280kHz as shown in the block diagram. The power switch is turned off by the output of the PWM comparator. A TTL low voltage will shut down the chip and high voltage enable the chip through EN pin. This pin may also be used to synchronize the part to nearly twice the base oscillator frequency. In order to synchronize to a higher frequency, a positive transition turns on the power switch before the output of the oscillator goes high, thereby resetting the oscillator. The synchronization operation allows multiple power supplies to operate at the same frequency. If synchronization is not used, this pin should be either tied high or left floating for normal operation.
Component Selection:
2 .7 V D C ~ 3 0 V D C L C IN
10uF VCC VSW FB 22uH
DF C OUT
22uF
V OUT
V IN
R2
E n a b le D SS
EN SS COMP
A M C 3202
AGND PGND
C SS C P2
200pF
R1
C P1 RP
5K
0 .1 u F
The AMC3202 develops a 1.276V reference from the FB pin to ground. Output voltage is set by connecting the FB pin to an output resistor divider and the maximum output voltage is determined by the VSW pin maximum voltage minus the output diode forward voltage. Referring to typical application circuit, the output voltage is set by the below formula (1):
R2 V OUT = 1 .276V 1 + R1
2.7VVOUT43VVF
(1)
where, VF is the output diode DF forward voltage. When choosing the inductor, one must consider factors such as peak current, core and ferrite material, output voltage ripple, EMI, temperature range, physical size, and cost. Lower values are chosen to reduce physical size of the inductor, and higher values reduce ripple voltage and core loss. In continuous conduction mode, the peak inductor current is equal to average current plus half of the ripple current, which should not cause inductor saturation. Based on the tolerance of the ripple current in the circuits, the following formula (2) can be referenced:
I Ripple =
V IN (VOUT - V IN ) fLV OUT
where, f = 280kHz.
(2)
In Boost circuits, the inductor becomes part of the input filter. In continuous mode, the input current waveform is triangular and does not contain a large pulsed current. This reduces the requirements imposed on the input capacitor selection. Capacitors in the range of 10uF to 100uF with an ESR less than 0.3 work well up to full 1.5A switch current.
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AMC3202
The VIN ripple is determined by the product of the inductor current ripple and the ESR of input capacitor, and the VOUT ripple comes from two major sources, namely ESR of output capacitor and the charging/discharging of the output capacitor. Ceramic capacitors have the lowest ESR, but too low ESR may cause loop stability problems. Aluminum Electrolytic capacitors exhibit the highest ESR, resulting in the poorest AC response. One option is to parallel a ceramic capacitor with an Aluminum Electrolytic capacitor.
Frequency Compensation
The goal of frequency compensation is to achieve desirable transient response and DC regulation while ensuring the stability of the system. A typical compensation network, as shown in the typical application circuit, provides a frequency response of two poles and one zero. The loop frequency compensation is performed on the output of the error amplifier (COMP pin) with a series RC network. The main pole is formed by the series capacitor and the output impedance of the error amplifier. The series resistor creates a zero, which improves loop stability and transient response. A second capacitor is sometimes used to reduce the switching frequency ripple on the COMP pin.
f P1 = f Z1 = f P2 = 1 2C P1 RO 1 2C P1 R P 1 2C P 2 R P
where, RO= error amplifier output resistance;
Soft Start
Through the addition of an external circuit, a soft-start function can be added to the AMC3202. Soft-start circuitry prevents the COMP pin from slamming high during startup, thereby inhibiting the inductor current from rising at a high slope. Referring to the figure shown in the following, the soft-start circuitry requires a minimum number of components and allows the soft-start circuitry to be activated any time when the EN pin is used to restart the converter.
V IN
5
EN V CC
V EN
D SS
4
4uA
3
SS
Q COMP
C
SS
1
C
C P1
P2
RP
Resistor RP and capacitors CP1 and CP2 form the compensation network. At turn on, the voltage at the COMP pin starts to come up, charging capacitor CSS through internal transistor Q, clamping the voltage at the COMP pin such that switching begins when COMP reaches the COMP threshold, typically 1.05V. Therefore, CSS slows down the startup of the circuit by limiting the voltage on the COMP pin. The soft-start time increases with the size of CSS. Diode DSS discharges CSS when the voltage on the EN pin is low. If the shutdown function is not used with this part, the cathode of DSS should be connected to VIN.
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PACKAGE
8-Pin Plastic S.O.I.C.
SYMBOLS A A1 A2 D E H L MIN. 0.053 0.002 0.189 0.150 0.228 0.016 0 MAX. 0.069 0.006 0.059 0.196 0.157 0.244 0.050 8
UNIT: INCH
THERMALLY ENHANCED DIMENSIONS PAD SIZE E1 D1 90X90E 0.081 REF 0.081 REF 95X13E 0.086 REF 0.117 REF
UNIT: INCH
NOTES: 1. JEDEC OUTLINE. N/A 2. DIMENSIONS "D" DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS AND GATE BURRS SHALL NOT EXCEED 15mm (.005in) PER SIDE. 3. DIMENSIONS "E" DOES NOT INCLUDE INTER-LEAD FLASH, OR PROTRUSIONS. INTER-LEAD FLASH AND PROTRUSIONS SHALL NOT EXCEED .25mm (.010in) PER SIDE.
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IMPORTANT NOTICE
ADDtek reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe property or environmental damage. ADDtek integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of ADDtek products in such applications is understood to be fully at the risk of the customer. In order to minimize risks associated with the customer's applications, the customer should provide adequate design and operating safeguards. ADDtek assumes to no liability to customer product design or application support. ADDtek warrants the performance of its products to the specifications applicable at the time of sale.
ADDtek Corp. 9F, No. 20, Sec. 3, Bade Rd., Taipei, Taiwan, 105 TEL: 2-25700299 FAX: 2-25700196
Copyright (c) 2006 ADDtek Corp. 11 DD074_B -AUGUST 2006

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