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TC25C25 TC35C25 BICMOS PWM CONTROLLERS
FEATURES
s s s s s s s s s s s s s Low Power BICMOS Construction Low Supply Current at 20 kHz ............... 1.0mA Typ Latch-Up Immunity ................. >500mA on Outputs Below Rail Input Protection .............................. - 5V High Output Drive ................................ 500mA Peak Fast Rise/Fall Time ..................... 50nsec @ 1000pF High Frequency Operation .................. Up to 1MHz Tri-state Sync Pin for Easy Parallel Operation Under Voltage Hysteresis Guaranteed Shutdown Pin Available Double-Ended Soft Start, With Small Cap Low Prop Delay Shutdown to Output ................................................. 140nsec Typ.
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 BiCMOSTM 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 "bootstrap" 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.
2 3 4 5
ORDERING INFORMATION
Part No. TC25C25EOE TC25C25EPE TC35C25COE TC35C25CPE Configuration Non-Inverting Pkg./Temperature 16-Pin SOIC (Wide) - 40C to +85C Non-Inverting 16-Pin Plastic DIP (Narrow) - 40C to +85C Non-Inverting 16-Pin SOIC (Wide) 0C to +70C Non-Inverting 16-Pin Plastic DIP (Narrow) 0C to +70C
FUNCTIONAL BLOCK DIAGRAM
VREF + VIN GND SYNC RT CT DISCH 16 15 12 3 6 5 7 R COMP 9 CMPTR S PWM LATCH IN- IN+ SOFT START SHUTDOWN 1 2 8 ERROR AMP +6V 50A R OSC FLIP FLOP UNDER VOLTAGE +4V REF OSC OUT 4 REFERENCE REGULATOR 35C25 13 VDD 11 A
6 7
+6V 14 B
10
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TC25/35C25-2 10/1/96
TELCOM SEMICONDUCTOR, INC.
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BICMOS PWM CONTROLLERS TC25C25 TC35C25
ABSOLUTE MAXIMUM RATINGS*
Supply Voltage ............................................................18V Maximum Chip Temperature ................................... 150C Storage Temperature ............................ - 65C to +150C Lead Temperature (10 sec) ..................................... 300C Package Thermal Resistance PDIP RJ-A ..................................................................... 125C/W PDIP RJ-C ........................................................................ 45C/W SOIC RJ-A ..................................................................... 250C/W SOIC RJ-A ........................................................................ 75C/W Operating Temperature 25C2x ........................................ - 40C TA +85C 35C2x ............................................. 0C TA +70C
*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.
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for - 40C < TA <
+85C for the TC25C25Exx; and 0C TC35C25Cxx; VIN and VDD = 16V; RT = 3.7k; CT = 1000pF; RD = 760. Parameter Reference Section
Output Voltage Line Regulation Load Regulation Temp Coefficient VREF Long Term Drift Short Circuit Output Noise TJ = 25C, IO = 1mA VIN = 8V to 18V II = 1mA to mA Note 1 Worst Case TJ = 25C, (Note 1) VREF to GND TJ = 25C, 10 Hz f 10 kHz, (Note 1) TJ = 25C, at 97 kHz VIN = 8V to 18V Note 1 TJ = 25C fosc = 100kHz, RL = 1M, (Note 1) TJ = 25C, RD = 0, (Note 1) CT = 100pF, RT = 1 RT Pin Tied to VREF, CT Pin at GND Sync Voltage = 4V, V(RT) = 4V TJ = 25C, Sync Amplitude = 5V, (Note 1) RT = 1, CT = 100pF, RD = 0, (Note 1) 3.9 -- -- -- 3.85 -- 20 -- -- -- -- 2.9 30 4.9 -- 1.8 -- -- 1.0 -- -- -- 70 0.7 -- 4.9 60 4 4 4 0.01 4 50 40 21 2 0.01 0.025 3.2 50 5.5 170 2.2 -- 130 -- 5 50 25 85 0.9 10 5.4 75 4.1 10 15 0.4 4.15 -- 70 -- 3 0.1 0.06 3.4 60 6.7 200 2.8 1 175 -- 15 200 100 -- 1.2 20 5.9 -- V mV mV mV/C V mV/1000Hrs mA V(rms) % %/V %/C V V nsec V A nsec MHz mV pA pA dB MHz mV V dB
Test Conditions
Min
Typ
Max
Units
Oscillator Section
Initial Accuracy Voltage Coefficient Temp Coefficient OSC Ramp Amplitude Reset Switch RDS (ON) Clock Amplitude Clock Min Width Sync Threshold Sync Input Current Min Sync Pulse Width Max OSC Freq Input Offset Voltage Input Bias Current Input Offset Current DC Open Loop Gain Gain Bandwidth Product Output Low Level Output High Level CMRR
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Error Amplifier Section (VCM = 2.5V)
TJ = 25C TJ = 25C RL = 100k Note 1 RL = 100k (N Channel) RL = 100k (NPN) VCM = 0.5 to 4.7V
TELCOM SEMICONDUCTOR, INC.
BICMOS PWM CONTROLLERS TC25C25 TC35C25
ELECTRICAL CHARACTERISTICS: Unless otherwise stated, these specifications apply for - 40C < TA <
+85C for the TC25C25Exx; and 0C TC35C25Cxx; VIN and VDD = 16V; RT = 3.7k; CT = 1000 pF; RD = 760 . Parameter
Supply Voltage Rejection Slew Rate Threshold Hysteresis
1
2 3 4 5 6 7
Test Conditions
VIN = 8V to 18V CLOAD = 50pF, ACL = 1 V(EA+) = 1V to 3V Pulse, (Note 1)
Min
90 -- -- 0.6 -- --
Typ
120 1 -- 0.8 1.2 250 -- 49 0.6 3.6 -- 46 30 1 20 140 2.4 13 20 55 40 2 7 2.2 75
Max
-- -- -- 1 2.5 350 0 -- 0.7 3.7 1 75 100 100 40 220 3 25 35 80 65 3 7.3 2.5 200
Units
dB V/sec V mA A % % V V A A mV nA nsec nsec V nsec nsec mA V V A
Total Standby Current
Supply Current Start-Up Current
PWM Comparator
Min. Duty Cycle Max Duty Cycle Input Threshold Input Threshold Input Bias Current Note 1, TJ = 25C TJ = 25C, fOSC = 100kHz, (Note 1) V(CT) = 0.6V V(CT) = 3.6V Note 1, TJ = 25C VSHUTDOWN = 0V VSHUTDOWN = 3V VSHUTDOWN = 3V VSHUTDOWN = 5V, (Note 1) VSHUTDOWN = 5V, (Note 1) -- 45 0.5 3.4 -- 30 -- -- -- 130 1.5 -- -- -- -- -- 6.45 1.7 --
Soft Start Section
Soft Start Current Soft Start Voltage Shutdown Input Current Min Shutdown Pulse Width Shutdown Delay Shutdown Threshold
Output Drivers (each output)
Output Low Level RDS (ON) Output High Level RDS (ON) Rise Time Fall Time ISINK = 20mA ISOURCE = 20mA CL = 1nF, (Note 1) CL = 1nF, (Note 1) fOSC = 100kHz
Power Supply
Supply Current UV Lockout Threshold UV Lockout Hysteresis Start-up Current
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.
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TELCOM SEMICONDUCTOR, INC.
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BICMOS PWM CONTROLLERS TC25C25 TC35C25
PIN CONFIGURATION (DIP AND SOIC)
IN- IN+ SYNC OSC OUT CT RT DISCHARGE SOFT START
1 2 3 4 5 6 7 8 TC25C25EPE TC35C25CPE
16 15 14 13 12 11 10 9
VREF + VIN OUTPUT B VDD GND OUTPUT A SHDN CMPTR
IN- IN+ SYNC OSC OUT CT RT DISCHARGE SOFT START
1 2 3 4 5 6 7 8 TC25C25EOE TC35C25COE
16 15 14 13 12 11 10 9
VREF + VIN OUTPUT B VDD GND OUTPUT A SHDN CMPTR
PIN DESCRIPTION
Pin No.
1 2 3 4 5 6 7
Symbol
IN- IN+ SYNC OSC OUT CT RT DISCHARGE
Description
Error Amplifier inverting input for output voltage reference input and amplifier gain set. Error Amplifier, non-inverting input for output voltage feedback to regulate voltage. Input pin for PWM controller oscillator synchronization of two or more controllers from an external clock output or from another PWM controller oscillator output. 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. Pin is the capacitor timing input to set oscillator frequency in conjunction with pin 6 RT timing resistor. Pin for timing resistor input to set oscillator frequency by setting the charge current into capacitor CT of pin 5. Pin for discharging the timing capacitor, CT 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. 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. Pin for compensation of the feedback loop response. 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. Pin for output drive of phase A to drive push pull transistor A. Pin for ground return for all inputs and output signals. Pin for power supply input to operate the output drivers A and B. Pin for output drive of phase B to drive push pull transistor B. Pin for voltage bias supply input for all PWM controller functions except output drive circuits. 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.
8 9 10 11 12 13 14 15 16
SOFT START CMPTR SHDN OUTPUT A GND VDD OUTPUT B V+ IN VREF
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TELCOM SEMICONDUCTOR, INC.
BICMOS PWM CONTROLLERS TC25C25 TC35C25
OUTPUT SECTION
The output stage of the TC35C25 is comprised of two pairs of complimentary CMOS drivers operating in a pushpull 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.
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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.
2 3 4
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/ F. SOFT START will mediate the start-up from under voltage recovery, power-on, or SHUTDOWN.
6 RT
RT TCx5C25 MASTER OSC OUT 4
SHUTDOWN
There is a minimum delay, non-latching shutdown feature 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.
5C T CT
GND 12
6
3 RT VREF SYNC SLAVE
RT 5C T CT
TCx5C25 GND 12
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 (RT, 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.
5 6 7
SLAVE TC > MASTER TC
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:
6 RT 5C T CT GND 12 RT TCx5C25 OSC OUT 4 MASTER
16 6 RT VREF
3 SYNC SLAVE
TCx5C25 5C T GND 12
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TELCOM SEMICONDUCTOR, INC.
BICMOS PWM CONTROLLERS TC25C25 TC35C25
OSCILLATOR FREQUENCY AND OUTPUT DEAD TIME
1/FO VDD PIN 5 TD 3V .5V ON-TIME (TCHG) PIN 4
0.5V 3V
+
ICHARGE 5 1.5V RT 6
1.5V
-
7 3 DISCH SYNC RD
CT
RT
OUTPUT DEAD TIME (TD)
The oscillator frequency (FO) =
1 TCHG + TD
V+ IN TO OUTPUT SHUTDOWN 1mA VON = 9.2V VOFF = 7V 75A
IS
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 (RT) 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
VIN 7V 9.2V
IS = STARTUP CURRENT
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 terminated.
Select a capacitor in the range of 100 pF to 1000 pF for CT. See graph in Typical Characteristic Curve. Calculate capacitor charging current (ICHG). ICHG =
2.5 x CT TCHG
CT in Farads, TCHG in seconds, ICHG in amperes, and RT in ohms. RT =
1.5 ICHG
The resistor (RD) controls the period of dead time (TD). During dead time this resistor (RD) current is the sum of the CT discharge current and the ICHG current. The value for RD can range from >1 to <900. Dead time increases when RD is increased. See graph in Typical Characteristic Curve for dead time resistor value.
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TELCOM SEMICONDUCTOR, INC.
BICMOS PWM CONTROLLERS TC25C25 TC35C25
BENCH TEST OPERATIONAL SIMULATION WAVEFORMS
3V 0.5V
5k
1
2
1 IN- IN+ SYNC OSC OUT CT RT DISCH SOFT VREF VIN OUTB VDD GND OUTA SHDN 16 15 14 13 12 11 10 .1f MET + - V011 16V 2 3 GND 4 5 MET 6
3.7k
CT PIN 5
PIN 2 VOLTAGE
OSC OUT PIN 4
DEAD TIME
1000pF
OUTPUT A PIN 11
7 0 to 1k 8
3 4 5 6 7
1000
CMPTR 9
OUTPUT B PIN 14
GND
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.
REPLACING BIPOLAR VERSIONS WITH CMOS
Although the pin-out and functions are the same for both the Bipolar and CMOS versions, there are several differences 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 RT and CT values are different for any particular frequency and dead-time requirement. The most important difference is that the absolute maximum rating of the VDD and VIN voltages for the TC35C25 is 18V, whereas the UC3525 is 40V.
TYPICAL CHARACTERISTICS
Oscillator Frequency vs. Ct and Rt
900 800 700 VDD = VIN = 16V, TA +25C Rt = 1k Rt = 2k Rt = 5k Rt = 10k Rt = 20k 40 35 30 VDD = 16V, TA +25C
Supply Current vs. Frequency
3000 2500
Dead Time vs. Ct and Discharge Resistor
VDD = 16V, TA +25C, Rt = 10k Ct = 1000pF
DEAD TIME (nsec)
CL = 2200pF CL = 1000pF CL = 470pF CL = 10pF
FOSC (kHz)
600 500 400 300 200 100 0 200 400 600 Ct (pF)
IDD (mA)
25 20 15 10 5
2000 1500 1000 500 0
Ct = 500pF Ct = 330pF Ct = 100pF
800
1000
0
0
0.2 0.4 0.6 0.8 FREQUENCY (MHz)
1
0
200 400 600 800 DISCHARGE RESISTOR ()
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