TC35C25

TC25C25 TELCOM | Alldatasheet

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4-111TELCOM SEMICONDUCTOR, INC. A VDD B OSC OUT CMPTR +6V 50µA ERROR AMP SYNC 3 C T DISCH 7 COMP 9 IN– 1 IN+ 2 SOFT START SHUTDOWN 10 GND 12 R T IN REFERENCE REGULATOR FLIP FLOP UNDER VOLTAGE OSC S R R +6V 35C25 PWM LATCH 16VREF +4V REF TC25/35C25-2 10/1/96 FUNCTIONAL BLOCK DIAGRAM TC25C25 TC35C25 BICMOS PWM CONTROLLERS GENERAL DESCRIPTION The TC35C25 family of PWM controllers are CMOS implementations of the industry standard 3525 voltage mode SMPS ICs. These second generation CMOS devices employ TelCom Semiconductors' Tough BiCMOS process for latch-up proof operation. They offer much lower power consumption than any of their previous CMOS or bipolar counterparts. These controllers have separate supply pins for the control and output sections of the circuit. This allows "boot- strap" operation. The CMOS output stage allows the output voltage to swing to within 25mV of either rail. Other improved features include tighter hysteresis and undervoltage start-up specifications over temperature, and very low input bias current on all inputs.

FEATURES

n Low Power BICMOS Construction n Tri-state Sync Pin for Easy Parallel Operation n Under Voltage Hysteresis Guaranteed n Shutdown Pin Available n Double-Ended n Soft Start, With Small Cap n Low Prop Delay Shutdown to

ORDERING INFORMATION

Part No. Configuration Pkg./Temperature TC25C25EOE Non-Inverting 16-Pin SOIC (Wide) – 40°C to +85°C TC25C25EPE Non-Inverting 16-Pin Plastic DIP (Narrow) – 40°C to +85°C TC35C25COE Non-Inverting 16-Pin SOIC (Wide) 0°C to +70°C TC35C25CPE Non-Inverting 16-Pin Plastic DIP (Narrow) 0°C to +70°C

4-112 TELCOM SEMICONDUCTOR, INC. ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for – 40°C < TA < +85°C for the TC25C25Exx; and 0°C <TA < +70°C for the TC35C25Cxx; VIN and VDD = 16V; RT = 3.7kΩ ; CT = 1000pF; RD = 760Ω. Parameter Test Conditions Min Typ Max Units Reference Section Output Voltage T J = 25°C, IO = 1mA 3.9 4 4.1 V Line Regulation V IN = 8V to 18V — ±4 ±10 mV Load Regulation I I = 1mA to mA — ±4 ±15 mV Temp Coefficient Note 1 — ±0.01 ±0.4 mV/ °C VREF Worst Case 3.85 4 4.15 V Long Term Drift T J = 25°C, (Note 1) — ±50 — mV/ 1000Hrs Short Circuit V REF to GND 20 40 70 mA Output Noise T J = 25°C, 10 Hz ≤ f ≥ 10 kHz, (Note 1) — 21 — µV(rms) Oscillator Section Initial Accuracy T J = 25°C, at 97 kHz — ±2 ±3% Voltage Coefficient V IN = 8V to 18V — ±0.01 ±0.1 %/V Temp Coefficient Note 1 — ±0.025 ±0.06 %/ °C OSC Ramp Amplitude 2.9 3.2 3.4 V Reset Switch RDS (ON) TJ = 25°C3 0 5 0 6 0 Ω Clock Amplitude f osc = 100kHz, RL = 1MΩ , (Note 1) 4.9 5.5 6.7 V Clock Min Width T J = 25°C, RD = 0Ω , (Note 1) — 170 200 nsec C T = 100pF, RT = 1Ω Sync Threshold R T Pin Tied to VREF, C T Pin at GND 1.8 2.2 2.8 V Sync Input Current Sync Voltage = 4V, V(R T) = 4V — — ±1 µA Min Sync Pulse Width T J = 25°C, Sync Amplitude = 5V, (Note 1) — 130 175 nsec Max OSC Freq R T = 1Ω , CT = 100pF, RD = 0Ω , (Note 1) 1.0 — — MHz Error Amplifier Section (VCM = 2.5V) Input Offset Voltage — ±5 ±15 mV Input Bias Current T J = 25°C— ±50 ±200 pA Input Offset Current T J = 25°C— ±25 ±100 pA DC Open Loop Gain R L = 100kΩ 70 85 — dB Gain Bandwidth Product Note 1 0.7 0.9 1.2 MHz Output Low Level R L = 100kΩ (N Channel) — 10 20 mV Output High Level R L = 100kΩ (NPN) 4.9 5.4 5.9 V CMRR V CM = 0.5 to 4.7V 60 75 — dB ABSOLUTE MAXIMUM RATINGS* Package Thermal Resistance Operating Temperature *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 perma- nent 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. BICMOS PWM CONTROLLERS TC25C25 TC35C25

4-113TELCOM SEMICONDUCTOR, INC. ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for – 40°C < TA < +85°C for the TC25C25Exx; and 0°C <TA < +70°C for the TC35C25Cxx; VIN and VDD = 16V; RT = 3.7kΩ ; CT = 1000 pF; RD = 760 Ω . Parameter Test Conditions Min Typ Max Units Supply Voltage Rejection V IN = 8V to 18V 90 120 — dB Slew Rate C LOAD = 50pF, ACL = 1 — 1 — V/ µsec V(EA+) = 1V to 3V Pulse, (Note 1) — — — Threshold Hysteresis 0.6 0.8 1 V Total Standby Current Supply Current — 1.2 2.5 mA Start-Up Current — 250 350 µA PWM Comparator Min. Duty Cycle Note 1, T J = 25°C— — 0 % Max Duty Cycle T J = 25°C, fOSC = 100kHz, (Note 1) 45 49 — % Input Threshold V(C T) = 0.6V 0.5 0.6 0.7 V Input Threshold V(C T) = 3.6V 3.4 3.6 3.7 V Input Bias Current Note 1, T J = 25°C— — ±1 µA Soft Start Section Soft Start Current V SHUTDOWN = 0V 30 46 75 µA Soft Start Voltage V SHUTDOWN = 3V — 30 100 mV Shutdown Input Current V SHUTDOWN = 3V — ±1 ±100 nA Min Shutdown Pulse Width V SHUTDOWN = 5V, (Note 1) — 20 40 nsec Shutdown Delay V SHUTDOWN = 5V, (Note 1) 130 140 220 nsec Shutdown Threshold 1.5 2.4 3 V Output Drivers (each output) Output Low Level RDS (ON) I SINK = 20mA — 13 25 Ω Output High Level RDS (ON) I SOURCE = 20mA — 20 35 Ω Rise Time C L = 1nF, (Note 1) — 55 80 nsec Fall Time C L = 1nF, (Note 1) — 40 65 nsec Power Supply Supply Current f OSC = 100kHz — 2 3 mA UV Lockout Threshold 6.45 7 7.3 V UV Lockout Hysteresis 1.7 2.2 2.5 V Start-up Current — 75 200 µA NOTE: 1. Not Tested. 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. BICMOS PWM CONTROLLERS TC25C25 TC35C25

4-114 TELCOM SEMICONDUCTOR, INC. TC25C25 TC35C25 BICMOS PWM CONTROLLERS PIN CONFIGURATION (DIP AND SOIC) 1 16 21 5 31 4 41 3 51 2 61 1 71 0 VDDOSC OUT IN+ IN– C T R T DISCHARGE SOFT START OUTPUT B IN VREF GND OUTPUT A SHDN CMPTR SYNC TC25C25EPE TC35C25CPE TC25C25EOE TC35C25COE VDDOSC OUT IN+ IN– C T R T DISCHARGE SOFT START OUTPUT B IN VREF GND OUTPUT A SHDN CMPTR SYNC PIN DESCRIPTION Pin No. Symbol Description 1I N – Error Amplifier inverting input for output voltage reference input and amplifier gain set. 2I N + Error Amplifier, non-inverting input for output voltage feedback to regulate voltage.

3 SYNC Input pin for PWM controller oscillator synchronization of two or more controllers from an

external clock output or from another PWM controller oscillator output. 4 OSC OUT Pin for output of the internal oscillator. This signal can be used as a master oscillator to sync other oscillators to run at the same timing period. 5C T Pin is the capacitor timing input to set oscillator frequency in conjunction with pin 6 RT timing resistor. 6R T Pin for timing resistor input to set oscillator frequency by setting the charge current into capacitor CT of pin 5. 7 DISCHARGE Pin for discharging the timing capacitor, C T of pin 5. During discharging time period, PWM controller output is disabled. This is called dead time. With a resistor between pin 7 and pin 5, the dead time can be controlled. 8 SOFT START Pin for soft starting the power supply. A capacitor from this pin to GND pin 12 will limit duty cycle till capacitor is charged above error amplifier output. 9 CMPTR Pin for compensation of the feedback loop response. 10 SHDN Pin for terminating both outputs of pins 11 and 14. This will shutdown the power supply outputs. A positive input with shutdown threshold of 2.4V is required for shutdown. 11 OUTPUT A Pin for output drive of phase A to drive push pull transistor A. 12 GND Pin for ground return for all inputs and output signals. 13 V DD Pin for power supply input to operate the output drivers A and B. 14 OUTPUT B Pin for output drive of phase B to drive push pull transistor B. 15 V +IN Pin for voltage bias supply input for all PWM controller functions except output drive circuits. 16 V REF Pin is the reference supply output voltage of 4.0 volts that may be used for any voltage reference purposes such as a reference to control output voltage.

4-115TELCOM SEMICONDUCTOR, INC. BICMOS PWM CONTROLLERS TC25C25 TC35C25 OSCILLATOR SYNCHRONIZATION WITH SEPARATE RC TIMER Synchronization can also be done by having a separate RC timing circuit on the slave oscillator that is slightly lower frequency than the master oscillator. The sync input will not be in a high impedance state so the number of slave oscillators is limited. This method of synchronization is useful when slave oscillator is located in a different location. When a separate RC timer is used in the slave controller, ground loop noise pickup in the oscillator is minimized. OUTPUT SECTION The output stage of the TC35C25 is comprised of two pairs of complimentary CMOS drivers operating in a push- pull mode. Each output is capable of sinking or sourcing nearly 500mA of peak current. They are also capable of absorbing just as much "kick-back" current without latching. SOFT START A soft restart recovery rate may be selected by placing a capacitor from SOFT START (pin 8) to ground. The calculation for the recovery timing is approximately 60 msec/ µF. SOFT START will mediate the start-up from under voltage recovery, power-on, or SHUTDOWN. SHUTDOWN There is a minimum delay, non-latching shutdown fea- ture on the TC35C25 PWM controller. Both outputs may be turned off by applying a positive voltage to SHUTDOWN (pin 10). Typical shutdown threshold is 2.4V. Returning the pin back to ground will reinitialize the soft start cycle. OSCILLATOR SECTION A tri-state feature has been added to accommodate systems which require multiple controllers to be run in a "master/slave" configuration. The timing resistor pin (R T, pin 6) may be tied to VREF to place the sync pin (SYNC, pin 3) in a high impedance state. This will allow the chip to be clocked from an external source. The sync output (OSC OUT, pin 4) of the TC35C25 can drive several sync inputs configured in this manner. OSCILLATOR SYNCHRONIZATION Synchronization of two TC35C25's can be done by making one PWM Controller as the master oscillator to synchronize the slave as follows: VREF OSC OUTC T GND R T C T GND R T TCx5C25 MASTER SLAVE C T SLAVE TC > MASTER TC C T R T R T TCx5C25 SYNC OSC OUTC T GND R T TCx5C25 C T GND R T TCx5C25 MASTER SLAVE C T R T SYNCVREF

4-116 TELCOM SEMICONDUCTOR, INC. TC25C25 TC35C25 BICMOS PWM CONTROLLERS The resistor (RD ) controls the period of dead time (TD ). During dead time this resistor (RD ) current is the sum of the C T discharge current and the ICHG current. The value for RD can range from >1Ω to <900Ω . Dead time increases when R D is increased. See graph in Typical Characteristic Curve for dead time resistor value. OSCILLATOR FREQUENCY AND OUTPUT DEAD TIME The oscillator frequency (FO ) = 1 TCHG + TD TCHG is the charging duration of CT. One of the PWM Controller output drivers is ON during charging of CT. TD is the output dead time when both of the output drivers are inactive. Resistor (R T) sets the Capacitor (CT) charging current. To choose an oscillator frequency (FO ), first select the period of dead time (TD ) required. Calculate the capacitor charge time (TCHG ). TCHG = 1 – FO x TC FO Select a capacitor in the range of 100 pF to 1000 pF for C T. See graph in Typical Characteristic Curve. Calculate capacitor charging current (ICHG ). C T in Farads, TCHG in seconds, ICHG in amperes, and R T in ohms. ICHG = 2.5 x CT TCHG R T = 1.5 ICHG 1mA TO OUTPUT SHUTDOWN IS VON = 9.2V VOFF = 7V 75µA 7V 9.2V IS = STARTUP CURRENT VIN IN C T DISCH R T 1.5V SYNC VDD ICHARGE ≈ 1.5V R T 1/FO TD 3V .5V ON-TIME (TCHG ) PIN 5 OUTPUT DEAD TIME (T D ) PIN 4 R D 3V0.5V UNDERVOLTAGE LOCKOUT SECTION The typical turn on threshold is 9.2V for operation of this family of PWM Controllers. When supply voltage at pin 15 drops below 7V, after normal operation above 9.2V, lockout occurs and both output drives to pin 11 and 14 are termi- nated.

4-117TELCOM SEMICONDUCTOR, INC. BICMOS PWM CONTROLLERS TC25C25 TC35C25 The 5k potentiometer sets a reference voltage at pin 2. When ramp voltage of pin 5 reaches this reference voltage, output drive pulse is active ON. Varying the discharge resistor will vary the dead time. Increasing the discharge resistor will effect an increase in the dead time. BENCH TEST OPERATIONAL SIMULATION WAVEFORMS OSC OUT PIN 4 PIN 2 VOLTAGE DEAD TIME 0.5V C T PIN 5 OUTPUT A PIN 11 OUTPUT B PIN 14 REPLACING BIPOLAR VERSIONS WITH CMOS Although the pin-out and functions are the same for both the Bipolar and CMOS versions, there are several differ- ences that need to be taken into account. The reference voltage on the TC35C25 is 4V instead of 5V and the oscillator ramp is 3V, not 4V. The R T and CT values are different for any particular frequency and dead-time require- ment. The most important difference is that the absolute maximum rating of the V DD and VIN voltages for the TC35C25 is 18V, whereas the UC3525 is 40V. VDD OUT B VIN VREF GND OUT A SHDN CMPTR OSC OUT SYNC IN+ IN– C T R T DISCH SOFT 1000pF MET 3.7k0 to 1k MET .1µf V011 16V GND GND TYPICAL CHARACTERISTICS 10.80.60.40.20 Supply Current vs. Frequency C L = 2200pF C L = 1000pF C L = 470pF C L = 10pF VDD = 16V, TA +25°C IDD (mA) FREQUENCY (MHz) Oscillator Frequency vs. Ct and Rt 100 200 300 400 500 600 700 800 900 1000800600400200 FOSC (kHz) C t (pF) R t = 1k R t = 2k R t = 5k R t = 10k R t = 20k VDD = VIN = 16V, TA +25°C 0 200 400 600 800 1000 3000DEAD TIME (nsec) 2500 2000 1500 1000 500 Dead Time vs. Ct and Discharge Resistor DISCHARGE RESISTOR ( Ω ) C t = 1000pF C t = 500pF C t = 330pF C t = 100pF VDD = 16V, TA +25°C, Rt = 10k