2120 Switched mode DC/DC-converter Switched mode DC/DC-converter

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2120 Switched mode DC/DC-converter Switched mode DC/DC-converter

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ISDN Remote Power Controller (IRPC)
2120
Switched mode DC/DC-converter Switched mode DC/DC-converter CCITT (I.430) ISDN compatible Integrated power
(only 2120-P P-DIP-22) power dissipation
Supply voltage range Input undervoltage detection Programmable overcurrent protection Soft start Control circuit achieve minimum start-up current Power housekeeping input Oscillator synchronization input/output Polarity reversal detection High voltage CMOS-technology
P-DSO-24-1
P-DIP-22
Type 2120-P 2120-T
Version
Ordering Code Q67100-H8645 Q67100-H6278
Package P-DIP-22 P-DSO-24-1 (SMD)
2120 Pulse Width Modulator (PWM) circuit designed fixed-frequency switching regulators especially telephony ISDN-environments. 2120 fully compatible with CCITT-power recommendations "S"-interface. Coupled with external components provide stable DC-supply subscriber terminals (TE's) network terminators (NT's). also programmed higher output voltages, e.g. supply S-lines with telephony ISDN-systems high conversion yield crucial maintain functionality supply conditions "S"- "U"-interfaces. 2120 design technology realizes high conversion efficiency power dissipation. should recognized that 2120 also used numerous DC/DC-conversion systems other than ISDN-power supplies.
Semiconductor Group
12.92
2120
Configurations (top view) P-DSO-24 P-DIP-22
Semiconductor Group
2120
Definitions Functions P-DSO P-DIP Symbol Input Output Definition Function
SYNC
Synchronization
Input synchronization oscillator external frequency, output synchronize multiple devices. external timing components ramp generator attached this pin. Error amplifier output Pulse Width Modulator (PWM) input loop stabilization network. Non-inverting input error amplifier.
RC-Oscillator
COMP
Compensation
N.C. N.C.
Positive Voltage Sense
Negative Voltage Inverting input error amplifier. Sense Soft Start Capacitor Emergency Polarity Detection Gate Drain Source Input Capacitor capacitor this determines soft-start characteristic. input voltage will activate output EME. input inverting Schmitt-trigger. Output FET-driver. Drain connection power FET. Source connection power FET.
connected input
buffer-capacitor current limiting charging-resistor.
Semiconductor Group
2120
Definitions Functions (cont'd) P-DSO P-DIP Symbol Input Output Definition Function
Enable Comparator output Comparator neg. input Comparator pos. input Ground External supply
high input voltage this will stop IRPC-function.
Connections universal usable comparator.
analog digital signals referred this pin. Output internal CMOS-supply. VEXT internal CMOS-circuits supplied from external DC-supply order reduce chip power dissipation. When voltage difference between these pins exceeds digital current limiting becomes active. Output reference voltage.
VEXT
VREF
Negative current sense Positive current sense Reference voltage Supply voltage
VBAT positive input voltage.
Semiconductor Group
2120
Figure IRPC Functional Diagram
Semiconductor Group
2120
Functional Description reference provides voltage regulation loop. high gain error amplifier compares reference voltage with switch mode supply output voltage. output error amplifier compared with periodic linear ramp, which generated sawtooth-oscillator circuit. comparator output fixed-frequency, variable pulse width logic signal, which passes through logic circuits high voltage power-switching-FET. digital current limiting device suppresses logic signal when voltage difference current limit sense input reaches this case control logic inhibits double pulses during oscillator period. Start-Up Procedure Before switched-mode DC/DC-converter starts, sequence several conditions passed order avoid system malfunction. primary undervoltage detection inhibits converter function. This insures that control functions have stabilized proper state when turn voltage (ca. reached, prevents start-up glitches. case connecting powered lines line powered charge current primary buffer capacitor limited external resistor (figure This resistor short-circuited 2120 when voltage drop across falls below approximately residual resistance this short-circuit about case primary undervoltage detection short-circuit will always deactivated. DC/DC-converter does start until charging primary buffer capacitor completed, maximum line input voltage reached. this feature desired, connected GND. this case primary current measuring circuit turns off, reduce chip-power dissipation from order avoid high current peaks during charging secondary capacitors line capacitors case supplying S-interface, soft start circuit implemented 2120. This circuit requires external capacitor, connected between GND. addition, enable input (ENA) allows external switch-on/switch-off control. DC/DCconverter disabled ENA, soft-start-capacitor discharged. This input also used several other functions, e.g. secondary overvoltage protection.
Semiconductor Group
2120
Figure DC/DC-Conversion 2120 contains SIPMOS-transistor power handling. Non-isolated isolated SMPSconfigurations possible. Logic analog circuits implemented CMOS order achieve power dissipation. error amplifier compares sensed voltage with reference attached thus controls Pulse Width Modulator (PWM). conversion frequency generated sawtooth oscillator which controlled external RC-components (figure external synchronization signal. 2120 synchronized rising edge sync signal, whose frequency must higher than free frequency, determined RC-components. SYNC-pin also used trigger-output. long capacitor sawtooth oscillator discharged, SYNC high. output processed control logic SIPMOS-transistor. control logic suppresses higher oscillations regulation loop caused e.g. case current limit detection. Semiconductor Group
2120
Polarity Detection Emergency conditions signaled reversed polarity line feeding voltage. When polarity reversal detected 2120, emergency conditions signaled microprocessor EME, which should shut down activity except simple telephony functions minimize power dissipation. polarity detection circuit also used other detection protection-functions, e.g. programmable primary undervoltage detection. Power Housekeeping integrated linear voltage regulator supplies internal circuits during start-up phase. Power dissipation this regulator reduced, auxiliary winding transformer external supply used that purpose connecting VEXT. input voltage VEXT reaches internal linear voltage regulator turns internal circuits from this external voltage. this case input current VEXT approx. Note: internal Zener-diode protects VEXT input against overvoltages. maximum Zener-current external supply isn't stabilized, input current must limited (e.g. resistor)! Interface Microprocessor 2120 offers TTL-compatible signals: (Emergency-output) becomes active, polarity reversal detected. output universal usable comparator; e.g.: generate microprocessor-reset signal.
Semiconductor Group
2120
2120 Applications ISDN-Environments Figure shows example wide application field 2120. network termination 2120 supplies internal IC's directly from U-interface. second IRPC, also powered from U-line, supplies S-interface main supply order. third IRPC used main supply regulate S-line feeding voltage. subscriber terminal 2120 used feeding internal circuits. 2120 accommodates both galvanically isolated non-isolated configuration. Considering diversity DC/DC-converter applications, this part specification only shows special ISDN-features 2120. switching frequency SMPS programmable external components. Figure shows switching frequency function minimum configuration able 2120 ISDN-applications using flyback converter (figure time constant soft start circuit programmed capacitor CSS. Figure shows primary start-up current limitation connecting CIN. reduce chip-powerdissipation, auxiliary winding transformer used switch internal linear CMOSsupply (pin VEXT). Polarity reversal detected POL. Figure shows realization microprocessor-reset-signal with universal usable comparator IRPC. Figure shows 2120 flyback configuration with transformer isolation. Figure shows 2120 flyback configuration with opto isolation, which useful high reliability galvanically isolated application.
Semiconductor Group
2120
Figure IRPC ISDN-Concept
Semiconductor Group
2120
Switching Frequency
Figure Switching Frequency Function
Semiconductor Group
2120
Figure 2120 Minimum Configuration
Semiconductor Group
2120
Figure Advanced IRPC-Application with Power Housekeeping Polarity Reversal Detection
Semiconductor Group
2120
According application figure output power will
Figure Generation µP-Reset Signal with 2120
Semiconductor Group
2120
Figure 2120 Flyback Configuration with Transformer Isolation
Semiconductor Group
2120
Figure 2120 Flyback Configuration with Opto Isolation Semiconductor Group
2120
Absolute Maximum Ratings (All references made P-DIP-22) Parameter Supply voltage (pin referred (pin Continuous drain current (pin Supply voltage VBAT (pin referred Analog/digital input voltage referred (pins Reference output current (pin Symbol Limit Values Unit
VBAT SYNC Tstg
VEXT input Z-current VEXT output current
SYNC-output current (pin Driver output current (pin Ambient temperature under bias Storage temperature Thermal resistance junction ambient
MOS-Handling: integrated SIPMOS-transistor (pin protected against electrostatic charges. input gate-source (pin must protected against Characteristics
Parameter Symbol min. Reference VREF Limit Values typ. max. Unit Test Condition
Output voltage Line regulation Load regulation Temperature stability Load current
VREF VREF Line VREF Load VREF IREF Load
3.92
4.08
Semiconductor Group
2120
Characteristics (cont'd) Parameter Symbol min. Limit Values typ. max. Unit Test Condition
Oscillator SYNC (pin1), (pin fOSC kHz, Initial accuracy Voltage stability fOSC Temperature stability fOSC Max. frequency H-sawtooth voltage L-sawtooth voltage H-sync output level L-sync output level 5.25
fmax
Error Amplifier COMP (pin (pin (pin Input offset voltage Input current Common mode range open loop gain Common mode rejection Unit gain bandwidth Supply voltage rejection H-output voltage L-output voltage
kCMR
0.02
VOFFSET
(pin)
Current Limit Comparator (pin 20), (pin Sense voltage Input current Input voltage range Response time signal (pin
VSense tRes
Semiconductor Group
2120
Characteristics (cont'd) Parameter Symbol min. Pulse Width Modulator Duty cycle Undervoltage Detection Start-up threshold Threshold hysteresis Soft Start (pin Charging current Limit Values typ. max. Unit Test Condition
Output Driver (pin Power H-output voltage H-output voltage L-output voltage Rise time Fall time Output current External Supply VEXT (pin Output voltage Output current Input voltage Z-current Enable Input (pin H-input voltage L-input voltage Response time signal (pin H-input current
ISource ISource ISink
tRes
5.25
Semiconductor Group
2120
Characteristics (cont'd) Parameter Symbol min. Comparator (pin 15), (pin 16), Input offset voltage Input bias current Input voltage range Response time signal (pin Limit Values typ. max. Unit Test Condition
tRes
Short Circuit (pin 12), Sense voltage
VSense (on)
VCIN)
Polarity Detection (pin (pin H-input voltage L-input voltage H-input current Response time signal (pin
tRes
5.25
Digital Outputs (pin (pin
IOUT
H-output voltage L-input voltage
5.25
Power (pin (pin 10), (pin
(on) toff
Leakage current Power consumption
(on) (off) ILeak Ptot
fOSC
Semiconductor Group

2120 Switched mode DC/DC-converter Switched mode DC/DC-converter

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