TC18C43 TC28C43 TC38C43 BiCMOS CURRENT MODE PWM CONTROLLERS 2 FEATURES GENERAL DESCRIPTION ■ ■ ■ ■ ■ ■ ■ The TC38C43 is a current mode BiCMOS PWM control IC. With a low 1.0 mA supply current along with high drive current (0.7A peak) it provides a low cost solution for a PWM that operates to 500 kHz and directly drives MOSFETs up to HEX 3 size. Performance of the oscillator and current sense amplifier have been greatly improved over previous bipolar versions. Voltage and temperature stability have been improved by a factor of 3. Noise immunity (PSRR) has also been improved. The TC38C43 is pin compatible with the earlier bipolar version so that designers can easily update older designs. Improvements have been added, though. For example, clock ramp reset current is specified at 2.5mA (±10%) for accurate dead time control. A few component values must be changed (RT & CT) to use the TC38C43 in existing bipolar designs. The 14-pin DIP and 16-pin SOIC versions have separate and internally isolated grounds, and are rated for higher output current (1.2A). These separate grounds allow for ‘bootstrap’ operation of the PWM to further improve efficiency. ■ ■ ■ ■ ■ ■ ■ Low Power BiCMOS Design Tough CMOSTM Construction Low Supply Current ............. 1.0mA Typ @ 100kHz Wide Supply Voltage Operation .............. 8V to 15V Latch-Up Immunity ................... 500mA on Outputs Input Will Withstand Negative Inputs to – 5 Volts High Output Drive .................................... 0.7A Peak (1.2A on 14-Pin and 16-Pin Versions) 2 kV ESD Protection Current Mode Control Fast Rise/Fall Time (Max) ........... 60nsec @ 1000pF High Frequency Operation ..........................500kHz Clock Ramp Reset Current ................. 2.5mA ±10% Low Propagation Delay Current Amp to Output ............................................ 140nsec Typ. Pin Compatible with UC3843 ORDERING INFORMATION Part No. Package Temperature TC18C43MJA TC18C43MJD 8-Pin CerDIP 14-Pin CerDIP TC28C43EOE TC28C43EPA TC28C43EPD 16-Pin SOIC (Wide) – 40°C to +85°C 8-Pin Plastic DIP – 40°C to +85°C 14-Pin Plastic DIP – 40°C to +85°C TC38C43COE TC38C43CPA TC38C43CPD 16-Pin SOIC (Wide) 8-Pin Plastic DIP 14-Pin Plastic DIP – 55°C to +125°C – 55°C to +125°C 0°C to +70°C 0°C to +70°C 0°C to +70°C CMPTR 1 VFB 2 ISENSE 3 RT / CT 4 8 TC18CMJA TC28CEPA TC38CCPA VREF 7 VIN 6 OUTPUT 5 GND 14-Pin Plastic DIP CMPTR 1 14 VREF NC 2 13 NC VFB 3 12 VIN NC 4 ISENSE 5 NC 6 9 GND RT / CT 7 8 POWER GND TC18CMJD TC28CEPD TC38CCPD 16-Pin SOIC (Wide) NC 1 16 NC NC 2 15 VREF CMPTR 3 14 VIN VFB 4 ISENSE 5 RT / CT 13 VDD 12 OUTPUT 6 11 GND NC 7 10 NC 8 9 POWER GND NC TC28CCOE TC38CEOE 11 VDD 3 4 5 FUNCTIONAL BLOCK DIAGRAM RT/CT VREF VIN 14 12 7 VREF OSC CLK 11 2.5V PIN CONFIGURATIONS 8-Pin Plastic DIP 1 UNDER VOLTAGE SECTION ANALOG GND 8 5 – + 2.5V POWER GROUND + 7 R ERROR AMP 3 OUTPUT PWM COMPARATOR + S Q – CLK VFB 10 UV GOOD 9 0.4V SENSE 6 VDD 1.4V LIMIT BUFFER 2R + – 1.4V – COMP 1 R PIN NUMBERS FOR 14-PIN DIP 10 OUTPUT 8 TC38C43-7 10/21/96 TELCOM SEMICONDUCTOR, INC. 4-93 BiCMOS CURRENT MODE PWM CONTROLLERS TC18C43 TC28C43 TC38C43 ABSOLUTE MAXIMUM RATINGS* Supply Voltage ............................................................18V Maximum Chip Temperature ................................... 150°C Storage Temperature ............................ – 65°C to +150°C Lead Temperature (Soldering, 10 sec) ................. +300°C Package Thermal Resistance CerDip RθJ-A ................................................ 150°C/W CerDip RθJ-C .................................................. 55°C/W PDIP RθJ-A ................................................... 125°C/W PDIP RθJ-C ..................................................... 45°C/W SOIC RθJ-A ................................................... 250°C/W SOIC RθJ-C ..................................................... 75°C/W Operating Temperature 18C4x ...................................... – 55C° ≤ TA ≤ +125°C 28C4x ........................................ – 40C° ≤ TA ≤ +85°C 38C4x ............................................. 0C° ≤ TA ≤ +70°C ELECTRICAL CHARACTERISTICS unless otherwise stated, these specifications apply over specific temperature range. VIN = VDD = 15V; RT = 71 kΩ; CT = 150 pF. TC18C43 TC28C43 TC38C43 Parameter Test Conditions Min Typ Max Min Typ Max Units TA = 25°C, IO = 1mA 9.5V ≤ VIN ≤ 15V, IO = 1mA 1mA ≤ lO ≤ 11mA (Note 1) 10Hz ≤ f ≤ 10 kHz,TA = 25°C (Note 1) TA = 125°C, 1000 Hrs. (Note 1) 4.9 — — — — — -20 5 ±3 ±5 ±0.25 100 ±0.5 -50 5.1 ±10 ±15 ±0.5 — — -100 4.90 — — — — — -30 5 ±3 ±3 ±0.25 100 ±0.5 -50 5.10 ±10 ±10 ±0.5 — — -100 V mV mV mV/°C µV(rms) % mA TA = 25°C (Note 4) 9.5V ≤ VIN ≤ 15V TMIN ≤ TA ≤ TMAX (Note 1); Figure 2 RT/CT Pin at 4V RT/CT Pin Peak to Peak Note 1 90 — — 2.25 2.45 1 100 ±0.2 ±0.01 2.5 2.65 — 110 ±0.3 ±0.05 2.75 2.85 — 93.8 — — 2.25 2.45 1 100 ±0.2 ±0.01 2.5 2.65 — 106.5 ±0.3 ±0.03 2.75 2.85 — kHz % %/°C mA V MHz V(CMPTR) = 2.5V (Note 1) 2V ≤ VO ≤ 4V (Note 1) 9.5V ≤ VIN ≤ 15V VFB = 2.7V, V(CMPTR) = 1.1V (Note 1) VFB = 2.3V, V(CMPTR) = 5V (Note 1) VFB = 2.3V, RL = 10k to Ground VFB = 2.7V, RL = 10k to VREF Note 1 Note 1 — — 70 650 80 1.2 3 5.65 0.1 — — ±15 ±0.3 90 750 100 1.5 3.4 6 0.7 5 3 ±50 ±2 — — — — — 6.5 1.1 7 5 — — 70 650 80 1.5 3.9 5.65 0.1 — — ±15 ±0.3 90 750 100 1.7 4.2 6 0.7 5 3 ±50 ±2 — — — — — 6.5 1.1 7 5 mV nA dB kHz dB mA mA V V µsec µsec Notes 2 & 3 V(CMPTR) = 5V (Note 2) 9.5V ≤ VIN ≤ 15V (Notes 1, 2 & 5) Note 1 V(ISENSE) = 1V (Note 1); Figure 3 2.8 0.85 70 — — 2.9 0.95 80 ±0.3 140 3.1 1.05 — ±2 160 2.8 0.85 70 — — 2.9 0.95 80 ±0.3 140 3.1 1.05 — ±2 150 V/V V dB nA nsec Reference Section Output Voltage Line Regulation Load Regulation Temp Stability Output Noise Voltage Long Term Stability Output Short Circuit Oscillator Section Initial Accuracy Voltage Stability Temp Stability Clock Ramp Reset Amplitude Maximum Freq Error Amp Section Input Offset Voltage Input Bias Current AVOL Gain Bandwidth Product PSRR Output Sink Current Output Source Current VOUT High VOUT Low Rise Response Fall Response Current Sense Section Gain Ratio Maximum Input Signal PSRR Input Bias Current Delay to Output 4-94 TELCOM SEMICONDUCTOR, INC. BiCMOS CURRENT MODE PWM CONTROLLERS TC18C43 TC28C43 TC38C43 1 ELECTRICAL CHARACTERISTICS (Cont): unless otherwise stated, these specifications apply over specified 2 temperature range. VIN = VDD = 15V; RT = 71 kΩ; CT = 150 pF. TC18C4X TC28C4X Parameter Test Conditions TC38C4X Min Typ Max Min Typ Max — — — — — — 7 11 40 30 6.5 — x8C43 x8C43 7.9 7.2 x8C43 (Note 1) TA = 25°C, VIN < VUV; Figure 1 VFB = V(ISENSE) = 0V; Figure 4 Units 15 20 60 60 — 18 — — — — — — 7 11 35 30 6.5 — 15 15 60 40 — 18 Ω Ω nsec nsec nC V 8.4 7.6 8.8 7.9 7.9 7.2 8.4 7.6 8.8 7.9 V V 95 97 100 0 95 97 100 0 % % 50 170 1 300 2 50 170 1 300 1.5 µA mA Output Section RDS (ON) (ON) Rise Time Fall Time Cross Conduction VDD Ma ISINK = 20mA ISOURCE = 20mA CL = 1nF (Note 1) CL = 1nF (Note 1) In Coulombs (Note 1) Note 1 RDS 3 Undervoltage Lockout Section Start Threshold Undervoltage Threshold 4 PWM Section Maximum Duty Cycle Minimum Duty Cycle Supply Current Start Up Operating where 0 ≤ V(ISENSE) ≤ 0.8V NOTES: 1. These parameters, although guaranteed over the recommended operating conditions, are not tested in production. 2. Parameter measured at trip point of latch. 3. Gain ratio is defined as: 5 4. Output frequency equals oscillator frequency for the x8C43. 5. PSRR of VREF, Error Amp and PWM Comparator combination. ∆VCOMP ∆V(ISENSE) TelCom Semiconductor reserves the right to make changes in the circuitry or specifications detailed in this manual at any time without notice. Minimums and maximums are guaranteed. All other specifications are intended as guidelines only. TelCom Semiconductor assumes no responsibility for the use of any circuits described herein and makes no representations that they are free from patent infringement. *Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to Absolute Maximum Rating Conditions for extended periods may affect device reliability. 6 PIN DESCRIPTION Pin No. 8-Pin Pin No 14-Pin Pin No 16-Pin Symbol Description 1 2 3 2 4 1 3 5 1 2 3 4 5 NC NC CMPTR VFB ISENSE 4 7 6 RT/CT No Connection No Connection Compensation of the feedback loop response. Feedback of voltage to error amplifier to regulate voltage. For sensing pass transistor current and terminate drive when current limit threshold is reached at this pin. Capacitor and resistor input to set oscillator frequency of this PWM controller. The resistor is connected from VREF output to RT/CT. The capacitor is connected from RT/CT to ANALOG GND. TELCOM SEMICONDUCTOR, INC. 7 8 4-95 BiCMOS CURRENT MODE PWM CONTROLLERS TC18C43 TC28C43 TC38C43 PIN DESCRIPTION (Cont.) Pin No. 8-Pin 5 6 7 8 Pin No 14-Pin Pin No 16-Pin Symbol 6 13 7 8 9 10 11 12 13 14 15 16 NC NC NC POWER GROUND ANALOG GND OUTPUT VDD VIN VREF NC 8 9 10 11 12 14 Description No Connection No Connection No Connection Ground return of output driver. For all the low level analog signal returns. Output to drive switching transistor gate input. Supply power input terminal for the output drivers. Voltage bias supply of all PWM Controller circuit functions. Reference: 5.0 volt output. No Connection. REFERENCE SECTION The reference is a zener-based design with a buffer amplifier to drive the output. It is unstable with capacitances between 0.01µF and 3.3µF. In a normal application a 4.7µF is used. In some lower noise layouts the capacitor can be eliminated entirely. The reference is active as soon as the 38C4x has power supplied. This is different than its bipolar counterparts, in that the bipolar reference comes on only after the IC has come out of its under voltage mode. Thus, on the 38C4x, the reference pin can not be used as a reset function such as on a soft start circuit. OSCILLATOR SECTION The oscillator frequency is set by the combination of a resistor from the reference to the RT/CT pin and by a capacitor from this pin to ground. The oscillator is designed to have ramp amplitude from 0.15 to 2.5 volts. This is approximate, as over shoot on the oscillator comparator causes the ramp amplitude to increase with frequency due to comparator delay. Minimum values for CT and RT are 33pF and 1kΩ respectively. Maximum values are dependent on leakage currents in the capacitor, not on the input currents to the RT/CT pin. fO ≈ 1 (RT in Ohms and CT in Farads) RT CT The value of RT affects the discharge current and the upper and lower comparators each have delays. As RT gets smaller and as the frequency of operation gets higher, the above equation is no longer valid. 14 VREF (5V) RT 7 RT/CT CT 9 GND PIN NUMBERS FOR 14-PIN DIP FREQUENCY OF OPERATION The frequency of oscillation for the TC38C43 is controlled by a resistor to VREF (RT) and a capacitor to ground (CT). VREF supplies current through the resistor and charges the capacitor until its voltage reaches the threshold of the upper comparator (≈2.5V). A 2.5mA current is then applied to the capacitor to discharge it to near ground (≈0.15V). The discharge current is then shut off and the cycle repeats. An approximate equation for the frequency of operation is: 4-96 TELCOM SEMICONDUCTOR, INC. BiCMOS CURRENT MODE PWM CONTROLLERS TC18C43 TC28C43 TC38C43 Dead Time The value of RT has an effect on the discharge rate but the primary consideration is the value of CT. The time required to discharge the capacitor is approximately 1000 CT. UNDERVOLTAGE LOCKOUT RANGE VIN Current is sensed through voltage drop across resistor RS. A small RC filter may be required to suppress switching transient. This voltage enters PWM Controller at ISENSE, pin 5. A voltage of 0.4 V is added before this is fed into PWM Comparator (+) input. The PWM Comparator (–) input senses the voltage feedback error amp output with a limit buffer that limits this voltage to 1.4V maximum. This limit buffer limits the peak current across RS to a maximum of 0.95V. In normal operation, the error amplifier controls the current limit threshold. SHUTDOWN METHODS TCx38C43 IS TCx8C43 VON = 8.4V VOFF = 7.6V TCx8C43 1mA CMPTR 4 5k 8.4 V 7.6V SHUTDOWN 9 5 5.1k Undervoltage Lockout Range The TCx8C43 PWM Controller is used where wide ranges of input voltage is not required. The range from starting Vin voltage threshold to under voltage threshold is approximately 9.5% of the starting voltage. The typical startup voltage is 8.4V and dropout voltage is 7.6V. This range is used most in DC-to-DC converter applications. Duty Cycle Limit The TCx8C43 PWM Controller has a duty cycle limit maximum of 99%. The oscillator is running at the same frequency as the output. ANALOG GND ISENSE SHUTDOWN 5 TO CURRENT SENSE RESISTOR Shutdown can be accomplished by either pulling ISENSE above 1 volt or pulling CMPTR, pin 1 to GND. This will set the PWM latch so that the output will remain low until the next clock pulse after the shutdown condition is removed. BENCH TEST OPERATIONAL SIMULATION CURRENT SENSE CIRCUIT 5 The timing ramp (RT/CT) is buffered by the emitter fullpower and fed back to the ISENSE input. This ramp simulates the dI/dT current ramp which would flow through the primary of the transformer. The output voltage of the power supply is simulated by feeding some of the reference voltage into VFB. The combination of the two levels determined the operating characteristics of the current mode controller. PWM COMPARATOR ISENSE R 0.4V – + + – RS C GND 9 3 TCx38C43 VREF VDD 2 1 14 170µA 1 6 7 LIMIT BUFFER 2R + 1.4V – ERROR AMP R PEAK CURRENT (IS) FORMULA: IS = 8 0.95V RS TELCOM SEMICONDUCTOR, INC. 4-97 BiCMOS CURRENT MODE PWM CONTROLLERS TC18C43 TC28C43 TC38C43 BENCH TEST OPERATIONAL SIMULATION RT 10k Q1 2N2222 OR EQUIV 5k 5k 1 CMPTR VREF 8 100k 4.7µF 2 IRAMP 3 4 10k VFB ISENSE RT/CT VIN OUTPUT GND 7 VDD (15V) 1µF 6 RL = 1k, 1W 5 GND CT TYPICAL CHARACTERISTICS Oscillator Frequency Changes vs. Temperature Start Current vs. Temperature VIN = VSTART ISTART (µA) VIN = 15V 140 MAX TYP 130 125 120 115 110 99 98 97 DELAY (nse c) 140 135 150 100 FREQUENCY (kHz) 145 ISENSE to Out Delay 101 150 130 120 110 100 105 MIN TYP 100 –60 –40 –20 0 20 40 60 80 100 120 140 TEMPERATURE (°C) 4-98 96 –60 –40 –20 0 20 40 60 80 100120 140 TEMPERATURE (°C) 90 –55 0 25 50 70 TEMPERATURE (°C) 125 TELCOM SEMICONDUCTOR, INC. BiCMOS CURRENT MODE PWM CONTROLLERS TC18C43 TC28C43 TC38C43 1 TYPICAL CHARACTERISTICS (Cont.) IDD vs. Temperature Frequency of Operation 2.0 10 nF 2 Dead Time vs. CT VIN = 15V f = 100kHz CT 1.6 1nF RT = 10 k RT = 22 k RT = 47 k RT = 100 k CT 1.8 IDD (mA) 10nF 1nF 3 1.4 1.2 100pF 1.0 –60 –40–20 0 20 40 60 80 100 120 140 10 kHz TEMPERATURE (°C) 100kHz FREQUENCY 1 MHz 100pF 100nsec 1 µsec DISCHARGE TIME 10µsec 4 1000 P D (mW) 800 PDIP SLOPE = – 8mW/°C CerDIP SLOPE = – 6.4mW/°C 600 5 400 200 0 25 SOIC SLOPE = – 4mW/°C 50 75 100 125 150 AMBIENT TEMPERATURE (°C) 6 7 8 TELCOM SEMICONDUCTOR, INC. 4-99