1.5A STEP DOWN SWITCHING REGULATOR 1.5A STEP DOWN CONVERTER OPERA

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1.5A STEP DOWN SWITCHING REGULATOR 1.5A STEP DOWN CONVERTER OPERA

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L4971
1.5A STEP DOWN SWITCHING REGULATOR
1.5A STEP DOWN CONVERTER OPERATING INPUT VOLTAGE FROM PRECISE 3.3V (±1%) INTERNAL REFERENCE VOLTAGE OUTPUT VOLTAGE ADJUSTABLE FROM 3.3V SWITCHING FREQUENCY ADJUSTABLE 300KHz VOLTAGE FEEDFORWARD ZERO LOAD CURRENT OPERATION INTERNAL CURRENT LIMITING (PULSE-BYPULSE HICCUP MODE) INHIBIT ZERO CURRENT CONSUMPTION PROTECTION AGAINST FEEDBACK DISCONNECTION THERMAL SHUTDOWN SOFT START FUNCTION DESCRIPTION L4971 step down monolithic power switching regulator delivering 1.5A voltage between 3.3V (selected simple external divider). Realized mixed technology, device uses internal power D-MOS transistor (with typical Rdson 0.25) obtain very high efficency high switching speed. TYPICAL APPLICATION CIRCUIT
Vi=8V 220µF 220nF 2.7nF
Minidip
SO16W
ORDERING NUMBERS: L4971 (Minidip) L4971D (SO16)
switching frequency 500KHz achievable (the maximum power dissipation packages must observed). wide input voltage range between output voltages regulated from 3.3V cover majority today's applications. Features this generations DC-DC converter include pulse-by-pulse current limit, hiccup mode short circuit protection, voltage feedforward regulation, soft-start, protection against feedback loop disconnection, inhibit zero current consumption thermal shutdown. device available plastic dual line, MINIDIP standard assembly, SO16W assembly.
L4971
126µH (77120) SB360 330µF VO=3.3V/1.5A
100nF
9.1K 22nF
100nF
D97IN748A
January 2001
1/12
L4971
BLOCK DIAGRAM
THERMAL SHUTDOWN VOLTAGES MONITOR CBOOT CHARGE SS_INH INHIBIT SOFTSTART 3.3V COMP INTERNAL REFERENCE INTERNAL SUPPLY 5.1V BOOT
3.3V
DRIVE
OSCILLATOR
CBOOT CHARGE LIGHT LOADS
D97IN594
CONNECTIONS
N.C.
D97IN596
N.C. N.C. COMP BOOT N.C. N.C.
SS_INH
D97IN595
COMP BOOT
SS_INH N.C. N.C.
Minidip
SO16W
FUNCTIONS
Name SS_INH Function Ground logic signal (active low) disables device (sleep mode operation). capacitor connected between this ground determines soft start time. When this grounded disables device (driven open collector/drain). external resistor connected between unregulated input voltage this capacitor connected from this ground switching frequency. (Line feed forward automatically obtained) Stepdown regulator output Unregulated input voltage capacitor connected between this allows drive internal DMOS Transistor output used frequency compensation Stepdown feedback input. Connecting directly this results output voltage 3.3V. external resistive divider required higher output voltages.
BOOT COMP
Pins internally, electrically connected die.
2/12
L4971
THERMAL DATA
Symbol th(j-amb) Parameter Thermal Resistance Junction ambient Max. Minidip SO16 Unit °C/W
Package mounted board.
ABSOLUTE MAXIMUM RATINGS
Symbol Minidip V6-V5 Ptot Tj,T S016 V5,V6 I5,I6 V12-V11 Bootstrap voltage Analogs input voltage (VCC 24V) Analogs input voltage (VCC 24V) (VCC 20V) Power dissipation Tamb 60°C Junction storage temperature Minidip SO16 Input voltage Output voltage Output peak voltage 0.1µs f=200KHz Maximum output current Parameter Value int. limit. -0.3 Unit
ELECTRICAL CHARACTERISTICS 25°C, Cosc 2.7nF, Rosc 20k, 24V, unless otherwise specified.) Specification Refered from 125°C
Symbol Parameter Test Condition Min. Typ. Max. Unit
DYNAMIC CHARACTERISTIC
Operating input voltage range Output voltage 50V; 1.5A 0.5A 1.5A 10V; 1.5A 3.3V; 1.5A Vcc+2VRMS; Vref; 1.5A; ripple 100Hz 125°C 3.33 3.292 3.22 3.36 3.36 3.36 0.44 3.39 3.427 0.55 0.88
SVRR
Dropout voltage Maximum limiting current Efficiency Switching frequency Supply voltage ripple rejection Voltage stability switching frequency Temp. stability switching frequency
Soft Start
Soft start charge current Soft start discharge current 3/12
Inhibit
level voltage Isource level
L4971
ELECTRICAL CHARACTERISTICS (continued)
Symbol Parameter Test Condition Min. Typ. Max. Unit
Characteristics
Iqop Iqst-by Total operating quiescent current Quiescent current Total stand-by quiescent current Duty Cycle 3.8V Vinh <0.9V 55V; Vinh <0.9V 3.33 2.5V 3.8V Vcomp 2.5V Vcomp 3.8V Vcomp Vfb; Icomp -0.1 0.1mA Vcomp 10.3 0.65 mV/°C
Error Amplifier
Voltage Feedback Input Line regulation Ref. voltage stability temperature High level output voltage level output voltage Source output current Sink output current Source bias current Supply voltage ripple rejection open loop gain Transconductance 3.36 3.39
source sink SVRR
Oscillator Section
Ramp Valley Ramp peak Maximum duty cycle Maximum Frequency Duty Cycle Rosc 13k, Cosc 820pF 0.78 0.85 2.15 0.92 10.2
4/12
L4971
Typical Performance (Using Evaluation Board) 100kHz
Output Voltage 3.3V 5.1V Output Ripple 10mV 10mV 12mV Efficiency =35V 1.5A Line Regulation 1.5A (VCC 55V) Load Regulation =35V 1.5A
Figure Test valuation board circuit.
Vi=8V 220µF 220nF 2.7nF
L4971
126µH (77120) SB360
VO=3.3V/1.5A
100nF
9.1K 22nF
100nF
330µF
D97IN749A
C1=220µF/63V C2=2.7nF C5=100nF C6=100nF C7=220nF/63V C8=330µF/35V Sanyo L1=126µH KoolMu 77120 Turns 0.5mm R1=20K R2=9.1K D1=GI SB360
L4971
VO(V) R3(K) R4(K)
Figure component layout figure
5/12
L4971
Figure Quiescent drain current input voltage.
(mA)
200KHz R1=22K C2=1.2nF 100KHz R1=20K C2=2.7nF
D97IN724
Figure Quiescent current junction temperature
(mA)
D97IN731
200KHz =22K =1.2nF 100KHz R1=20K C2=2.7nF
VCC=35V
Tamb=25°C
Vcc(V)
Tj(°C)
Figure Stand-by drain current input voltage
Ibias (µA)
Tj=125°C Vss=GND Tj=25°C
D97IN732
Figure Line Regulation
3.377
Tj=125°C
D97IN733
3.376 3.375
Tj=25°C
3.374 3.373 3.372 3.371 3.370 VCC(V) VCC(V)
Figure Load regulation
3.378 3.376
D97IN734
Figure Switching frquency
(KHz)
D97IN784
VCC=35V
Tamb=25°C
3.374
Tj=25°C
Tj=125°C
3.372 3.370 3.368 3.366 3.364 3.362 3.360 IO(A)
3.3n
4.7n
5.6n
R1(K)
6/12
L4971
Figure Switching Frequency input voltage.
(KHz) 107.5 105.0 102.5 100.0 97.5 95.0 92.5 90.0 VCC(V)
Tj=25°C
D97IN735
Figure Switching frequency junction temperature.
(KHz)
D97IN785
Tj(°C)
Figure Dropout voltage between
D97IN736
Figure Efficiency output voltage.
100KHz
D97IN737
Tj=125°C
200KHz
IO(A)
Tj=-25°C
VCC=35V IO=1.5A
VO(V)
Figure Efficiency output current.
VCC=24V VCC=12V
D97IN738
Figure Efficiency output current.
=12V VCC=24V VCC=8V
D97IN739
VCC=8V
IO(A)
CC=48V fsw=100KHz VO=5.1V
VCC=48V
fsw=100KHz VO=3.36V
7/12
L4971
Figure Efficiency output current.
CC=48V CC=12V VCC=24V
D97IN740
Figure Efficiency output current.
VCC=48V fsw=200KHz VO=3.36V VCC=8V VCC=12V CC=24V
D97IN741
VCC=8V
fsw=200KHz O=5.1V
O(A)
IO(A)
Figure Efficiency Vcc.
V0=5 .1V-f
Figure Power dissipation Vcc.
D97IN742
Pdiss (mW)
VO=5.1V fsw=100KHz
D97IN743
0KHz
IO=1.5A IO=1A
3.36
IO=0.5A
IO=1.5A
VCC(V)
VCC(V)
Figure Efficiency
Pdiss (mW)
VCC=35V fsw=100KHz
D97IN744
Figure Pulse pulse limiting currentvs. junction temperature.
Ilim
fsw=100KHz VCC=35V
D97IN747
IO=1.5A
IO=1A
IO=0.5A
V0(V)
Tj(°C)
8/12
L4971
Figure Load transient.
Figure Line transient.
100KHz
D97IN786
(mV) -100
1ms/DIV
Figure Soft start capacitor selection inductor Vccmax.
(µH)
fsw=100KHz
D97IN745
Figure Soft start capacitorselection Inductor Vccmax.
(µH)
D97IN746
680nF 470nF
fsw=200KHz
56nF
330nF
47nF
220nF
33nF
22nF
100nF
VCCmax(V)
VCCmax(V)
Figure Open loop frequency phase error amplifier
GAIN (dB)
GAIN
D97IN787
Phase
-100
Phase
-150 -200
f(Hz)
9/12
L4971
DIM. MIN. 3.18 7.95 2.54 7.62 7.62 5.08 3.81 1.52 0.125 0.51 1.15 0.356 0.204 1.65 0.55 0.304 10.92 9.75 0.313 TYP. 3.32 0.020 0.045 0.014 0.008 MAX. MIN.
inch TYP. 0.131 MAX.
OUTLINE MECHANICAL DATA
0.065 0.022 0.012 0.430 0.384 0.100 0.300 0.300 0.260 0.200 0.150 0.060
Minidip
10/12
L4971
DIM. MIN. 0.25 2.35 0.33 0.23 10.1
TYP. MAX. 2.65 0.51 0.32 10.5 1.27 10.65 0.75 1.27 0.394 0.010 0.016 MIN. 0.093 0.004 0.013 0.009 0.398 0.291
inch TYP. MAX. 0.104 0.012 0.020 0.013 0.413 0.299 0.050 0.419 0.030 0.050
OUTLINE MECHANICAL DATA
(min.)8° (max.)
SO16 Wide
11/12
L4971
Information furnished believed accurate reliable. However, STMicroelectronics assumes responsibility consequences such information infringement patents other rights third parties which result from use. license granted implication otherwise under patent patent rights STMicroelectronics. Specification mentioned this publication subject change without notice. This publication supersedes replaces information previously supplied. STMicroelectronics products authorized critical components life support devices systems without express written approval STMicroelectronics. logo registered trademark STMicroelectronics 2001 STMicroelectronics Printed Italy Rights Reserved STMicroelectronics GROUP COMPANIES Australia Brazil China Finland France Germany Hong Kong India Italy Japan Malaysia Malta Morocco Singapore Spain Sweden Switzerland United Kingdom U.S.A. http://www.st.com
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1.5A STEP DOWN SWITCHING REGULATOR 1.5A STEP DOWN CONVERTER OPERA

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