UNISONIC TECHNOLOGIES CO., LTD TL5 PULSE-WIDTH-MODULATION CONTROL CIRCUITS DESCRIPTION The UTC TL5 incorporates on a single monolithic chip all the functions required for a pulse width modulation (PWM) control circuit. Designed primarily for power-supply control, It contains an error amplifier, a regulator, an oscillator, a PWM comparator with a dead-time-control input, undervoltage lockout (UVLO), short-circuit protection (SCP) and an open-collector output transistor. The error-amplifier common-mode voltage ranges from V to.5v. The noninverting input of the error amplifier is connected to a -V reference. Dead-time control (DTC) can be set to provide % to % dead time by connecting an external resistor between DTC and GND. The oscillator frequency is set by terminating RT with an external resistor to GND. During low V CC conditions, the UVLO circuit turns the output off until V CC recovers to its normal operating range. FEATURES * Complete PWM power control * 3.6-V to 4-V operation * Internal under voltage-lockout circuit * Internal short-circuit protection * Oscillator frequency : khz to 5kHz * Variable dead timer provides control over total range ORDERING INFORMATION Ordering Number Lead Free Halogen Free Package Packing TL5L-D8-T TL5G-D8-T DIP-8 Tube - TL5G-S8-R SOP-8 Tape Reel - TL5G-S8-T SOP-8 Tube of 3 Copyright 4 Unisonic Technologies Co., Ltd
TL5 MARKING DIP-8 SOP-8 PIN CONFIGURATION UNISONIC TECHNOLOGIES CO., LTD of 3
TL5 ABSOLUTE MAXIMUM RATINGS PARAMETER SYMBOL RATINGS UNIT Supply Voltage (Note ) V CC 4 V Amplifier Input Voltage V I(FB) V Output Voltage V OUT 5 V Output Current I OUT ma Output Peak Current I O(PEAK) ma Continuous Total Power Dissipation See dissipation rating table Operating Ambient Temperature Range T OPR - ~ +85 C Storage Temperature Range T STG -65 ~ +5 C Note:. All voltage values are with respect to the network ground terminal.. Absolute maximum ratings are those values beyond which the device could be permanently damaged. Absolute maximum ratings are stress ratings only and functional device operation is not implied. DISSIPATION RATING TABLE PACKAGE T A 5 C POWER RATING DERATING FACTOR ABOVE T A =5 C T A =7 C POWER RATING T A =7 C POWER RATING T A =7 C POWER RATING DIP-8 mw 8.mW/ C 64mW 5mW mw SOP-8 75mW 5.8mW/ C 464mW 377mW 45mW RECOMMENDED OPERATING CONDITIONS PARAMETER SYMBOL MIN MAX UNIT Supply Voltage V CC 3.6 4 V Amplifier Input Voltage V I(FB).5 V Output Voltage V OUT 5 V Output Current I OUT ma COMP Source Current 45 μa COMP dc Load Resistance kω Oscillator Timing resistor R T 5 5 kω Oscillator Frequency f OSC 5 khz Operating Ambient Temperature Range T A - 85 C UNISONIC TECHNOLOGIES CO., LTD 3 of 3
TL5 ELECTRICAL CHARACTERISTICS OVER RECOMMENDED OPERATING FREE-AIR TEMPERATURE RANGE (, f OSC =khz, all typical values at T A =5 C, unless otherwise noted) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT REFERENCE Output Voltage V OUT COMP Connected to FB.95.5 V Input Regulation V CC =3.6V ~ 4V.5 mv Output Voltage Change with Temperature T A = - C ~ 5 C - - T A = 5 C ~ 85 C - mv/v UNDERVOLTAGE LOCKOUT Upper T A = 5 C 3 V Threshold Voltage Lower V THR T A = 5 C.8 V Reset T A = 5 C..55 V Hysteresis T A = 5 C mv SHORT CIRCUIT PROTECTION SCP Threshold voltage T A = 5 C.95..5 V SCP Voltage, Latched No pullup 4 85 3 mv SCP Voltage, UVLO Standby No pullup 6 mv Input Source Current T A = 5 C - -5 - μa SCP Comparator Threshold Voltage.5 V OSCILLATOR Frequency f R T =k khz Standard Deviation of Frequency 5 khz Frequency Change with Voltage V CC =3.6V ~ 4V khz T A = -4 C ~ 5 C -4 -.4 4 khz Frequency Change with Temperature T A = - C ~ 5 C -4 -.4 4 khz T A = 5 C ~ 85 C -4 -. 4 khz Voltage at R T V RT V DEAD-TIME CONTROL Output (source) Current I O(SOURCE) V (DT) =.5V (Note).9*I RT.*I RT μa Input Threshold Voltage V I(THR) Duty cycle=%.5.7 Duty cycle=%.3.5 V ERROR AMPLIFIER Input Voltage V IN V CC =3.6V ~ 4V.5 V Input Bias Current I I(BIAS) -6-5 na Output Voltage Swing Positive.5.3 V V O(SW) Negative.3.4 V Open-Loop Voltage Amplification G V 8 db Unity-Gain Bandwidth.5 MHz Output (sink) Current I O(SINK) V I(FB) =.V, COMP=V 6 μa Output (source) Current I O(SOURCE) V I(FB) =.8V, COMP=V -45-7 μa OUTPUT Output Saturation Voltage V O(SAT) I OUT =ma.5 V Off-State Current I OFF V OUT =5V,Vcc= V OU T=5V μa Short-Circuit Output Current I O(SC) V OUT =6V 4 ma TOTAL DEVICE Standby Supply Current (Off state) I STN-BY.5 ma Average Supply Current R T =k.4. ma Note: Output source current at R T UNISONIC TECHNOLOGIES CO., LTD 4 of 3
TL5 SCHEMATIC FOR TYPICAL APPLICATION VIN + TSP + VOUT 5 SCP V CC VOUT 6 7 DTC RT COMP UTC TL5 GND 8 FB 3 4 FUNCTIONAL BLOCK DIAGRAM UNISONIC TECHNOLOGIES CO., LTD 5 of 3
TL5 DETAILED DESCRIPTION VOLTAGE REFERENCE A.5-V regulator operating from V CC is used to power the internal circuitry of the TL5 and as a reference for the error amplifier and SCP circuit. A resistive divider provides a -V reference for the error amplifier non-inverting input which typically is within % of nominal over the operating temperature range. ERROR AMPLIFIER The error amplifier compares a sample of the dc-to-dc converter output voltage to the -V reference and generates an error signal for the PWM comparator. The dc-to-dc converter output voltage is set by selecting the error amplifier gain (see Fig. ), using the following expression. V OUT = (+R/R) (V) The error-amplifier output is brought out as COMP for use in compensating the dc-to-dc converter control loop for stability. Because the amplifier can only source 45µA, the total dc load resistance should be kω or more. OSCILLATOR/PWM The oscillator frequency (f OSC ) can be set between khz and 5kHz by connecting a resistor between RT and GND.Acceptable resistor values range from 5 kω to 5 kω. The oscillator frequency can be determined by using the graph shown in Fig. 5. The oscillator output is a triangular wave with a minimum value of approximately.7v and a maximum value of approximately.3v. The PWM comparator compares the error-amplifier output voltage and the DTC input voltage to the triangular wave and turns the output transistor off whenever the triangular wave is greater than the lesser of the two inputs. UNISONIC TECHNOLOGIES CO., LTD 6 of 3
TL5 DETAILED DESCRIPTION(Cont.) DEAD TIME CONTORL (DTC) DTC provides a means of limiting the output-switch duty cycle to a value less than %, which is critical for boost and flyback converters. A current source generates a reference current (IDT) at DTC that is nominally equal to the current at the oscillator timing terminal, RT. Connecting a resistor between DTC and GND generates a dead-time reference voltage (VDT), which the PWM/DTC comparator compares to the oscillator triangle wave as described in the previous section. Nominally, the maximum duty cycle is % when VDT is.7v or less and % when VDT is.3v or greater. Because the triangle wave amplitude is a function of frequency and the source impedance of RT is relatively high(5ω),choosing RDT for a specific maximum duty cycle, D, is accomplished using the following equation and the voltage limits for the frequency in question as found in Fig. (V OSC(MAX) and V OSC(MIN) are the maximum and minimum oscillator levels): R DT =(R T +5)[D(V OSC(MAX) -V OSC(MIN) )+V OSC(MIN) ] Where R DT and R T are in ohms, D in decimal Soft start can be implemented by paralleling the DTC resistor with a capacitor (C DT ) as shown in Fig.. During soft start, the voltage at DTC is derived by the following equation: V DT I DT R DT (-e (-t/rdtcdt) ) CDT 6 DTC UTC RDT TL5 Fig. Soft- Start Circuit If the dc-to-dc converter must be in regulation within a specified period of time, the time constant, RDTCDT, should be t/3 to t/5.the UTC TL5 remains off unit VDT.7V, the minimum ramp value. CDT is discharged every time UVLO or SCP becomes active. UNDERVOLTAGE-LOCKOUT (UVLO) PROTECTION The undervoltage-lockout circuit turns the output transistor off and resets the SCP latch whenever the supply voltage drops too low (approximately 3V at 5 ) for proper operation. A hysteresis voltage of mv eliminates false triggering on noise and chattering. UNISONIC TECHNOLOGIES CO., LTD 7 of 3
TL5 DETAILED DESCRIPTION(Cont.) SHORT-CIRCUIT PROTECTION (SCP) The UTC TL5 includes short-circuit protection (see Fig. 3), which turns the power switch off to prevent damage when the converter output is shorted. When activated, The SCP prevents the switch from being turned on until the internal latching circuit is reset. The circuit is reset by reducing the input voltage until UVLO becomes active or until the SCP terminal is pulled to ground externally. When a short circuit occurs, the error-amplifier output at COMP rises to increase the power-switch duty cycle in an attempt to maintain the output voltage. SCP comparator starts an RC timing circuit when COMP exceeds.5v.if the short is removed and the error-amplifier output drops below.5v before time out, normal converter operation continues. If the fault is still present at the end of the time-out period, the time sets the latching circuit and turns off the UTC TL5 output transistor..5v RSCP 85kΩ CSCP 5 SCP From Error Amp.5V scp Comparator Q kω scp Comparator VREF=V To Output Drive Logic Q Fig. 3 SCP Circuit The timer operates by charging an external capacitor (C SCP ),connected between the SCP terminal and ground, towards.5v through a 85k resistor (R SCP ).The circuit begins charging from an initial voltage of approximately 85mV and times out when capacitor voltage reaches V.The output of SCP comparator then goes high, turns on Q,and latches the timer circuit. The expression for setting the SCP time period is derived from the following equation: V SCP =(.5-.85)(-e -t/ )+.85 Where =R SCP C SCP The end of the time-out period, t SCP, occurs when V SCP =V. Solving for C SCP yields: C SCP =.46*t SCP Where t is in seconds, C in µf t SCP must be much longer (generally to 5 times) than the converter start-up period or the converter will not start. OUTPUT TRANSISTOR The output of the UTC TL5 is an open-collector transistor with a maximum collector current rating of ma and a voltage rating of 5V.The output is turned on under the following conditions: the oscillator triangle wave is lower than both the DTC voltage and the error-amplifier output voltage, the UVLO circuit is inactive, and the short-circuit protection circuit is inactive. UNISONIC TECHNOLOGIES CO., LTD 8 of 3
TL5 PARAMETER MEASUREMENT INFORMATION UNISONIC TECHNOLOGIES CO., LTD 9 of 3
TL5 APPLICATION INFORMATION V IN 5V GND C μf V + R 47Ω Q TPS L μh C3.μF C4 μf + C4.μF R 56kΩ R3 43kΩ 5 6 7 SCP DTC RT V CC V OUT COMP UTC TL5 GND 8 FB 3 4 CR MBRS4T3 C μf V C6.μF R4 5.kΩ + R5 7.5kΩ % R6 3.4kΩ % R7.kΩ 3.3V GND C7.47μF Partial Bill of Materials: Q TPS Texas Instruments L CTX- or Coiltronics 3 turns of #8 wire on Micrometals No. T5-6B core C TPSD 7MR AVX C TPSD 7MR AVX CR MBRS 4T3 Motorola NOTES: A. Frequency = KHz B. Duty cycle = 9% max C. Soft-start time constant (TC) = 5.6ms D. SCP TC = 7msA Fig. 5 Step-Down Converter UNISONIC TECHNOLOGIES CO., LTD of 3
TL5 TYPICAL CHARACTERISTICS M Oscillator Frequency vs Timing Resistance Oscillator Frequency vs Ambient Temperature Oscillator Frequency, fosc (Hz) DT Resistance=R T TA=5 C Oscillator Frequency, fosc(hz) 98 96 k 94 9 k k k Timing Resistance, R T ( ) M 9 DT Resistance=k R T =k 88-5 -5 5 5 75 Ambient Temperature, T A ( C) Reference Output Voltage, VREF(V) Reference Output Voltage vs Power -Supply Voltage.8.6 T A =5 C FB and COMP.4 Connected Together..8.6.4. 3 4 5 6 7 8 9 Power-Supply Voltage, V CC (V) Reference Output Voltage Fluctuation, VREF (%).6.4. -. -.4 -.6 Reference Output Voltage Fluctuation vs Ambient Temperature FB and COMP Connected Together -.8-5 -5 5 5 75 Ambient Temperature, T A ( C) Average Supply Current, ICC(mA) Average Supply Current vs Power -Supply Voltage.5 R T =k T A =5 C Average Supply Current, ICC (ma) Average Supply Current vs Ambient Temperature.3...9.5 3 Power-Supply Voltage, V CC (V) 4.8 DT Resistance=k R T =k -5-5 5 5 75 Ambient Temperature, T A ( C) UNISONIC TECHNOLOGIES CO., LTD of 3
TL5 TYPICAL CHARACTERISTICS(Cont.) Triancle Wave Amplitude Voltage, PWM (V).8.5 PWM Triangle Wave Amplitude Voltage vs Oscillator Frequency T A =5 C 3.5.5.6.3 Error Amplifier Output Voltage, VOUT(V) Error Amplifier Output Voltage vs Output(Sink)Current T A =5 C V I(FB) =.V. V OSC(MAX) (% duty cycle).9 V OSC(MIN) (zero duty cycle).5 k k M M..4.6 Oscillator Frequency, f OSC (Hz) Output(Sink)Current, I OUT (ma) 3 Error Amplifier Output Voltage vs Output(Source)Current.46 Error Amplifier Output Voltage vs Ambient Temperature.5.45.44 Error Amplifier Output Voltage, VOUT (V).5 VO- Error Amplifier Output Voltage -V.43.4.5 T A =5 C V I(FB) =.8V 4 6 8 Output(Source)Current, I OUT (ua).4 V I(FB) =.8V No Load.4-5 -5 5 5 75 Ambient Temperature, T A ( C) Error Amplifier Output Voltage, VOUT (V) 4 Error Amplifier Output Voltage vs Ambient Temperature V I(FB) =.V No Load Error Amplifier Open -Loop Gain, GV(dB) Error Amplifier Open-Loop Gain and Phase Shift vs Frequency 4-8 3 T A =5 C - Error Amplifier Open -Loop Gain, GV (db) -4 8 G V -7 6-3 4 - -33-5 -5 5 5 75 Ambient Temperature, T A ( C) - k k M Frequency, f(hz) -36 M UNISONIC TECHNOLOGIES CO., LTD of 3
TL5 TYPICAL CHARACTERISTICS(Cont.) Output Duty Cycle-% Output Duty Cycle vs DTC Voltage T A =5 R T =Ω 8 6 tscp-scp Time-Out Period -ms Scp-Time-Output Period vs SCP Capacitance 8 6 4.5.5 DTC Voltage -V 4 T A =5 R T =Ω DT Resistance =kω 4 6 8 Cscp-scp Capacitance -nf DTC Output Current, IO(DT) (μa) -6-5 -4-3 - - DTC Output Current vs RT Output Current T A =5 DT Voltage =.3V Output Saturation Voltage, VCE (V) Output Saturation Voltage vs Output (Sink) Current.5.5 T A =5 - - -3-4 -5 RT Output Current, I OUT (μa) -6 5 5 Output(Sink)Current, I O(SINK) (ma) UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice. UNISONIC TECHNOLOGIES CO., LTD 3 of 3