HIGH PERFORMANCE CURRENT MODE CONTROLLERS Power Management Power Manag
|
|
|
Top Searches for this datasheet
GM3842A, GM3843A, GM3844A, GM3845A
HIGH PERFORMANCE CURRENT MODE CONTROLLERS Power Management Power Management
GM384XA series high performance fixed-frequency current mode controllers. They specially designed off-Line DC-to-DC converter applications. They require minimal external components precisely tailor performance wide variety applications. These GM384XA series include trimmed oscillator precise duty cycle control, temperature-compensated reference, high gain error amplifier, current-sensing comparator, high-current totem pole output driving power MOSFET. On-chip protection features include undervoltage lockouts with hysteresis both input reference, cycle-by-cycle current limiting, programmable output deadtime, latch single pulse metering. this simple DIP-8 SOP-8 package!
Features
Start-Up Operating Current Automatic Feed Forward Compensation Current Mode Operating Frequency 500kHz Trimmed Oscillator Discharge Current Precise Duty Cycle Control Latching Cycle-By-Cycle Current Limiting Undervoltage Lockout with Hysteresis High Current Totem Pole Output
(on)/10V(off); GM3843A GM3845A have UVLO thresholds 8.4V (on)/ 7.6V (off). GM3842A GM3843A operate within 100% duty cycle; GM3844A GM3845A operate within duty cycle.
SIMPLIFIED BLOCK DIAGRAM
Vref VREF Undervoltage LOCKOUT OSCILLATOR Error Amplifier
5.0V REFERENCE
Undervoltage LOCKOUT
Output Latching Power Ground Current Sense Input
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A GM3844A have UVLO thresholds
Voltage Feedback Input Output Compensation
www.gammamicro.com
PRELIMINARY
Revision Mar. 2004
GM3842A, GM3843A, GM3844A, GM3845A MARKING INFORMATION CONFIGURATIONS (TOP VIEW)
(SO-8)
VREF
OUTPUT
VREF
OUTPUT
GM384X
COMP ISENSE COMP
GM384X
ISENSE
ORDERING INFORMATION
GM3842A, GM3843A, GM3844A, GM3845A
Ordering Number
GM3842AS8T GM3842AS8R GM3842AD8T GM3843AS8T GM3843AS8R GM3843AD8T GM3844AS8T GM3844AS8R GM3844AD8T GM3845AS8T GM3845AS8R GM3845AD8T
Package
DIP-8 DIP-8 DIP-8 DIP-8
Shipping
Units/ Tube 2,500 Units/ Tape Reel Units/ Tube Units/ Tube 2,500 Units/ Tape Reel Units/ Tube Units/ Tube 2,500 Units/ Tape Reel Units/ Tube Units/ Tube 2,500 Units/ Tape Reel Units/ Tube
detail Ordering Number identification, please last page.
GM3842A, GM3843A, GM3844A, GM3845A
ABSOLUTE MAXIMUM RATINGS
PARAMETER
Supply Voltage (low impedance source) Output Current, Source Sink Input Voltage (analog inputs pins Maximum Power Dissipation (TA= 25°C) Error Output Sink Current Operating Junction Temperature Storage Temperature Range Lead Temperature (soldering sec.)
Note: Maximum Package Power Dissipation Limits must observed.
SYMBOL
ISINK(E.A) Tstg
VALUE
±1.0
UNIT
PACKAGE DESCRIPTION
lead FUNCTION COMP ISENSE Output VREF FUNCTION This Error Amplifier output made available loop compensation. This inverting input Error Amplifier. normally connected switching power supply output through resistor divider. voltage proportional inductor current connected this input. uses this information terminate output switch conduction. Oscillator frequency maximum Output cycle programmed connecting resistor VREF capacitor ground. This combined control circuitry power ground. This output directly drives gate power MOSFET. Peak current 1.0A sourced sunk this pin. This positive supply control integrated circuit (IC) This reference output. provides charging current capacitor through resistor
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A, GM3843A, GM3844A, GM3845A
Power Management
REPRESENTATIVE BLOCK DIAGRAM
Vref 2.5V Internal Baias
Reference Regulator
UVLO
3.6V Vref UVLO
Oscillator
(Toggle flip flop used only GM3844A, GM3845A)
Output
Vref 1.0mA
1.0V Current Sense Comparator Latch Current Sense Input Power Ground
GM3842A, GM3843A, GM3844A, GM3845A
Voltage Feedback Input Output Compensation Error Amplifier
Sink Only Positive True Logic
TIMING DIAGRAM
Capacitor
Latch "Set" Input Output/ Compensation Current Sense Input Latch "Reset" Input
Output Latch Small Small Latch
GM3842A, GM3843A, GM3844A, GM3845A
ELECTRICAL CHARACTERISTICS
70°C, *VCC=15V, CT=3.3nF, RT=10kW, unless otherwise specified
CHARACTERISTICS
Reference Section Reference Output Voltage Line Regulation Load Regulation Short Circuit Output Current Oscillator Section Oscillation Frequency Frequency Change with Voltage Oscillator Amplitude Error Amplifier Section Input Bias Current Input Voltage Open Loop Voltage Gain Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Output Voltage Current Sense Section Current Sense Input Voltage Gain Maximum Input Signal Supply Voltage Rejection Input Bias Current Output Section Output Voltage
SYMBOL
TEST CONDITIONS
UNIT
VREF DVREF DVREF
25°C, IREF= IREF 20mA TA=25°C 25°C (Peak Peak)
-100
-180
DVCC V(OSC) IBIAS VI(EA) AVOL PSRR ISINK ISOURCE VI(MAX) IBIAS
0.05
VFB= VPIN1=2.5V -0.5
-0.1 -1.0
2.58
VPIN2=2.7V, VPIN1=1.1V VPIN2=2.3V, VPIN1=5V VPIN2=2.3V, RL=15kW VPIN2=2.7V, RL=15kW PIN8 (Note VPIN1=5V (Note (Note VPIN3=3V ISINK= 20mA ISINK= 200mA ISOURCE= 20mA ISOURCE= 200mA 25°C, 1nF(Note 25°C, 1nF(Note
2.85
-3.0
3.15
0.08 13.5
High Output Voltage Rise Time Fall Time Undervoltage Lockout Section Start Threshold Minimum Operating Voltage (after
VTH(ST) VOPR(MIN)
GM3842A, GM3844A GM3843A, GM3845A GM3842A, GM3844A GM3843A, GM3845A
14.5
16.0
17.5 11.5
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A, GM3843A, GM3844A, GM3845A
ELECTRICAL CHARACTERISTICS (Continued)
70°C, *VCC=15V, CT=3.3nF, RT=10kW, unless otherwise specified
CHARACTERISTICS
Section Maximum Duty Cycle Minimum Duty Cycle Total Standby Current Start-Up Current Operating Supply Current Zener Voltage
SYMBOL
TEST CONDITIONS
UNIT
D(MAX) D(MIN) ICC(OPR)
GM3842A, GM3843A GM3844A, GM3845A
GM3842A/ 43A/ 44A/ VPIN3= VPIN2=0V ICC= 25mA
0.17
Adjust above Startup threshold before setting Note1: Parameter measured trip point latch with VPIN2 Note2: Gain defined A=DVPIN1 DVPIN3 VPIN3 0.8V
Note3: These parameters, although guaranteed, 100% tested production
GM3842A, GM3843A, GM3844A, GM3845A
TYPICAL PERFORMANCE CHARACTERISTICS
(KW)
1000pF 200pF 10pF VCC= TA=25°C 500pF
VCC= TA=25°C
10pF 500pF 200pF 1000pF
fosc (kHz)
fosc (kHz)
Figure Timing Resistor Oscillator Frequency
Figure Output Dead-Time Oscillator Frequency
GM3842A, GM3843A, GM3844A, GM3845A
TYPICAL PERFORMANCE CHARACTERISTICS
Dmax
VCC= 3.3nF TA=25°C
(dB)
VCC= 100K 25°C
(kW)
100k
(Hz)
Figure Maximum Output Duty Cycle Timing Resistor (GM3842A/43A)
Figure Error Open-Loop Gain Frequency
VCC=
125°C 25°C
(mA)
VCC=
Figure Current Sense Input Threshold Error Output Voltage
(°C)
Figure Reference Short Circuit Current Temperature
Vsat
80µs Pulsed Load 120Hz Rate
(mA) ISense=
Sourse Saturation (Load Ground) VFB= 25°C 3.3nF GM3843A/ Sink Saturation (Load VCC) (mA) VCC(V) Figure Output Saturation Voltage Load Current 25°C Figure Supply Current Supply Voltage
VCC=
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A/
GM3842A, GM3843A, GM3844A, GM3845A OPERATING DESCRIPTION
GM3842A, GM3843A, GM3844A GM3845A high performance, fixed frequency, current mode controllers. They designed off-ine DC-to-DC converter applications offering great versatility with minimal external components. representative block diagram shown page
Oscillator
oscillator frequency determined values timing components Capacitor charged from reference through resistor approximately discharged internal current sink. During oscillator generates internal blanking pulse that holds center input gate high. This causes output state, thus producing controlled amount Figure show versus oscillator frequency Figure Output deadtime versus frequency, both given values output deadtime. Note that many different values will give same oscillator frequency, only combination will yield specific output deadtime given frequency. oscillator thresholds temperature compensated, These interned circuit vefinements minimizes variations oscillator frequency maximum output duty cycle. many noise sensitive applications desirable frequency-lock converter external system clock. This accmplished applying clock signal circuit shown Figure best locking results, free-unning oscillator frequency about less than clock frequency. method multi unit synchronization shown Figure very accurate output duty cycle clamping tweaking clock waveform.
Error Amplifier
GM384XA series have fully compensated error amplifier with access both inverting input output, providing voltage gain (typical). noninverting input internally biased pinned out. converter output voltage typically divided down monitored inverting input. maximum input bias current -2.0 which cause output voltage error that equal product input bias current equivalent input divider source resistance. Error Amplifier Output (Pin allows external loop compensation. output voltage offset diode drops divided three before connects inverting input Current Sense Comparator. This assures that drive pulses appear Output (Pin when lowest state (VOL). This happens when power supply operating load removed, beginning softstart interval (Figures 12). Error minimum feedback resistance limited amplifier's source current (0.5 required output voltage (VOH) reach comparator's clamp level:
Rf(min) 3.0(1.0V) 1.4V 8800W 0.5mA
GM3842A, GM3843A, GM3844A, GM3845A
Current Sense Comparator Latch
GM384XA series operate current mode controller, whereby output switch conduction initiated oscillator terminated when peak inductor current reaches threshold level established Error Amplifier Output/Compensation (Pin1). error signal controls peak inductor current cycle-by-cycle basis. Current Sense Comparator Latch configuration assures that only single pulse appears Output during given oscillator cycle. inductor current converted voltage inserting groundreferenced sense resistor series with source output switch This voltage monitored Current Sense Input (Pin compared level derived from Error Output. peak inductor current under normal operating conditions controlled voltage where:
Ipk= V(PIN1) 1.4V
When power supply output overloaded output voltage sensing lost, chip operation normal. these situations, Current Sense Comparator threshold will internally clamped maximum peak switch current
1.0V Ipk(mak)=
GM3842A, GM3843A, GM3844A, GM3845A
When designing high power switching regulator become desirable reduce internal clamp voltage order keep reasonable level power dissipation Adjusting internal clamp voltage very simple, shown Figure external diodes compensate internal diodes constant clamp voltage over temperature. Avoid much reduction Ipk(max) clamp voltage, will noise pickup erratic results. narrow spike leading edge current waveform often occurs cause power supply instability when output load light. This spike caused power transformer interwinding capacitance output rectifier recovery time. eliminate this problem adding filter Current Sense Input, with time constant similar spike's duration; Figure
Undervoltage Lockout
UVLO comparators GM384XA series assure that chips fully functional before output stage enabled. positive power supply terminal (VCC) reference output (Vref) each have separate comparators. Each built-in hysteresis prevent erratic output behavior their thresholds reached. comparator upper lower thresholds V/10 GM3842A GM3844A, 8.4V/7.6V GM3843A GM3845A. Vref comparator upper lower thresholds 3.6V/3.4 large hysteresis startup current GM3842A GM3844A makes them ideal off-line converter applications where efficient bootstrap startup required. GM3843A GM3845A intended lower voltage DC-to-DC converter applications. zener connected shunt regulator form ground. purpose protect from excessive voltage that occur during system startup. minimum operating voltage GM3842A GM3844A 11V; GM3843A GM3845A 8.2V.
Output
GM384XA series have single totem pole output stage that designed direct drive power MOSFETs. provides ±1.0 peak drive current typical rise fall time with load. Additional internal circuitry keeps output sinking mode whenever UVLO active. This eliminates need external pull-down resistor.
Reference
bandgap reference trimmed ±1.0% tolerance 25°C GM384XA series. primary purpose supply charging current oscillator timing capacitor. reference short circuit protection provide more than 20mA powering additional control system circuitry.
Design Considerations
make your converter using wire-wrap plug-in prototype boards. High-frequency circuit layout techniques must observed prevent pulsewidth jitter. This usually caused excessive noise pick-up imposed Current Sense Voltage Feedback inputs. improve noice immunity lowering circuit impedances these points. layout should have ground plane with low-current signal highcurrent switch output grounds returning separate paths input filter capacitor. Ceramic bypass capacitors (0.1 connected directly VCC, Vref required, depending upon circuit layout, provide impedance path filtering high frequency noise. high-current loops should short possible heavy copper runs minimize radiated EMI. Error compensation circuitry converter output voltage divider should placed close possible GM384XA, possible from power switch other noise- generating components.
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A, GM3843A, GM3844A, GM3845A
Current mode converters exhibit subharmonic oscillations when operating duty cycle greater than with continuous inductor current. This instability independent regulators closed-loop characteristics caused simultaneous operating conditions fixed frequency peak current detecting. Figure shows phenomenon graphically. switch conduction begins, causing inductor current rise slope This slope function input voltage divided inductance. Current Sense Input reaches threshold established control voltage. This causes switch turn current decay slope until next oscillator cycle. unstable condition shown pertubation added control voltage, resulting small (dashed line). With fixed oscillator period, current decay time reduced, minimum current switch turn-on (t2) increased m2/m1. minimum current next cycle (t3) decreases m2/m1) (m2/m1). This pertubation multiplied m2.m1 each succeeding cycle, alternately increasing decreasing inductor current switch turn-on. Several oscillator cycles required before inductor current reaches zero causing process commence again. m2/m1 greater than converter will unstable. Figure shows that adding artificial ramp that synchronized with clock control voltage, pertubation will decrease zero succeeding cycles. This compensation ramp (m3) must have slope equal slightly greater than m2/2 stability. With m2/2 slope compensation, average inductor current follows control voltage yielding true current mode operation. compensating ramp derived from oscillator added either Voltage Feedback Current Sense inputs (Figure
GM3842A, GM3843A, GM3844A, GM3845A
Control Voltage Inductor Current Oscillator Period
Control Voltage
Oscillator Period Figure Continuous Current Waveforms Inductor Current
GM3842A, GM3843A, GM3844A, GM3845A
Figure External Clock Synchronization
Vref Internal Bias
Oscillartor
External Sync Input
0.01
Error Amplifier
diode clamp required Sync amplitude large enough cause bottom side more than below ground.
Figure External DUTY CYCLE CLAMP multi-unit synchronization
5.0k 5.0k 5.0k Internal Bias
Oscillator
Error Amplifier
Additional GM384XA series
1.44 2RB)
Dmax
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A, GM3843A, GM3844A, GM3845A
Figure Adjustable reduction clamp level
Vclamp=
1.67
+0.33X10-3
Vref Internal Bias Oscillator
IPK(max)= where:
Vclamp Vclamp 1.0V
Vclamp Error Amplifier 1.0mA 1.0V
Comp/ Latch
GM3842A, GM3843A, GM3844A, GM3845A
Figure Soft-start circuit
Internal Bias
Vref
Oscillator
Error Amplifier
1.0mA
1.0V
1.0M
tsoft-start 3600C
GM3842A, GM3843A, GM3844A, GM3845A
Figure Adjustable buffered reduction clamp level with soft-start
Vclamp=
1.67
IPK(max)= where:
Vclamp Vclamp 1.0V
Internal Bias
Vref
tsoftstart=
3Vclamp
Oscillator
Vcalmp Error Amplifier 1.0V 1.0mA
Comp/ Latch
MPSA63
Figure Current sensing power mosfet
VPIN
RDS(on) RDS(on)
Vref
SENSEFET= MTP10N10M Then VPIN 0.075
SENSEFET
proper operation during over current conditions, reduction Ipk(max) clamp level must implemented. Refer Figures 1.0V Comp/ Latch
Power Ground Input Source Retum
1/4W Control Circuitry Ground
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A, GM3843A, GM3844A, GM3845A
Figure current wavefrom spike suppression
Vref
GM3842A, GM3843A, GM3844A, GM3845A
Comp/ Latch
1.0V
addition filter will eliminate instability caused leading edge spike current waveform.
GM3842A, GM3843A, GM3844A, GM3845A
Figure MOSFET Parasitic Oscillations
VREF
Comp/ Latch
Figure Isolated MOSFET Drive
2.5V
1.0mA
Error compensation circuit stabilizing current-mode topology except boost flyback converters operating with continuous inductor current.
GM3842A, GM3843A, GM3844A, GM3845A
Series gate resistor will damp high frequency parasitic oscillations caused MOSFET input capacitance series wiring inductance gate-source circuit.
GM3842A, GM3843A, GM3844A, GM3845A
Figure Latched Shutdown
Bias 1.0mA
MCR101 2N3905 2N3903
GM3842A, GM3843A, GM3844A, GM3845A
MCR101 must selected holding less than (min). simple transistor circuit used place shown. resistors
Figure Error Amplifier Compensation
2.5V
1.0mA
Error compensation circuit stabilizing current-mode boost flyback topologies operating with continuous inductor current.
GM3842A, GM3843A, GM3844A, GM3845A SOP-8(SO-8) PACKAGE OUTLINE DIMENSIONS
0.0285 0.0105 0.725 0.275
Layout
0.060 1.52
0.238 0.008 6.04 0.155 0.004 3.94
0.275
0.155
INDENT
0.008 0.002 0.203 0.05
0.057 0.004 1.45 0.007 0.003 0.175 0.075
0.024
0.050 1.270
0.05 1.27
0.693 0.504 4.91
Inches
0.063 0.006 1.60 0.15
0.016 0.004 0.175 0.075
DIP-8 PACKAGE OUTLINE DIMENSIONS
0.252 0.008 6.40
0.362 0.008 9.20
0.134 0.008 3.40 0.158 0.012 4.01
0.02 0.51
0.13 0.008 3.30
Inches
0.008 7.62
0.012 0.004 0.304 0.3425 0.0155 8.70
0.018 0.004 0.46 0.10
0.008 2.54 0.06 0.01 1.524 0.15
GM3842A, GM3843A, GM3844A, GM3845A
GM3842A, GM3843A, GM3844A, GM3845A
ORDERING NUMBER
3842
Gamma Micro. Circuit Type Package SO-8 DIP-8 Shipping Tape Reel
Version
GM3842A, GM3843A, GM3844A, GM3845A
Other recent searches
SP6126 - SP6126 SP6126 Datasheet
SN74HC259 - SN74HC259 SN74HC259 Datasheet
SN54HC259 - SN54HC259 SN54HC259 Datasheet
S6680ZOV511RA450 - S6680ZOV511RA450 S6680ZOV511RA450 Datasheet
DS229 - DS229 DS229 Datasheet
CMPD6001 - CMPD6001 CMPD6001 Datasheet
CMPD6001A - CMPD6001A CMPD6001A Datasheet
CMPD6001C - CMPD6001C CMPD6001C Datasheet
CMPD6001S - CMPD6001S CMPD6001S Datasheet
BAT54S2 - BAT54S2 BAT54S2 Datasheet
AD7312 - AD7312 AD7312 Datasheet
Privacy Policy | Disclaimer
© 2012 Datasheet Archive
