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ISL6842, ISL6843, ISL6844, ISL6845
Data Sheet October 2003 FN9124.1
Improved Industry Standard Single Ended Current Mode PWM Controller
The ISL6842, ISL6843, ISL6844, ISL6845 family of adjustable frequency, low power, pulse width modulating (PWM) current mode controllers is designed for a wide range of power conversion applications including boost, flyback, and isolated output configurations. Peak current mode control effectively handles power transients and provides inherent over-current protection. This advanced BiCMOS design is pin compatible with the industry standard 384x family of controllers and offers significantly improved performance. Features include low operating current, 60A start-up current, adjustable operating frequency to 2MHz, and high peak current drive capability with 20ns rise and fall times.
Features
* 1A MOSFET gate driver * 60A startup current, 100A maximum * 30ns propagation delay current sense to output * Fast transient response with peak current mode control * Adjustable switching frequency to 2MHz * 20ns rise and fall times with 1nF output load * Trimmed timing capacitor discharge current for accurate deadtime/maximum duty cycle control * High bandwidth error amplifier * Tight tolerance voltage reference over line, load, and temperature * Tight tolerance current limit threshold
Ordering Information
PART NUMBER ISL6842IB ISL6842IU ISL6843IB ISL6843IU ISL6844IB ISL6844IU ISL6845IB ISL6845IU TEMP. RANGE (oC) -40 to 105 -40 to 105 -40 to 105 -40 to 105 -40 to 105 -40 to 105 -40 to 105 -40 to 105 PACKAGE 8 Ld SOIC 8 Ld MSOP 8 Ld SOIC 8 Ld MSOP 8 Ld SOIC 8 Ld MSOP 8 Ld SOIC 8 Ld MSOP PKG. DWG. # M8.15 M8.118 M8.15 M8.118 M8.15 M8.118 M8.15 M8.118
Applications
* Telecom and Datacom Power * Wireless Base Station Power * File Server Power * Industrial Power Systems * PC Power Supplies * Isolated Buck and Flyback Regulators * Boost Regulators
Pinout
ISL6842, ISL6843, ISL6844, ISL6845 (8-PIN SOIC, MSOP) TOP VIEW
COMP 1 FB 2 CS 3 RTCT 4 8 VREF 7 VDD 6 OUT 5 GND
NOTE: Add -T to part number for Tape and Reel packaging.
PART NUMBER ISL6842 ISL6843 ISL6844 ISL6845
RISING UVLO 14.4V 8.4V 14.4V 8.4V
MAX. DUTY CYCLE 100% 100% 50% 50%
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures. 1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc. Copyright (c) Intersil Americas Inc. 2003. All Rights Reserved. All other trademarks mentioned are the property of their respective owners.
Functional Block Diagram
V DD UVLO COMPARATOR + BG + GND A 2.5 V A=0.5 VDD OK ENABLE
VREF 5.00 V
VREF
VREF FAULT
+
+ BG
2
CS FB COMP VREF RTCT
VREF UV COMPARATOR 4.65V 4.80V
ISL6842, ISL6843, ISL6844, ISL6845
PWM COMPARATOR 100mV + + -
ERROR AMPLIFIER + -
2R
1.1V CLAMP R
ISL6844/5 ONLY Q T Q OUT SQ
2.6V 0.7V ON OSCILLATOR COMPARATOR + 8.4mA ON
RQ RESET DOMINANT
CLOCK P/N -42, -44 -43, -45 UVLO ON/OFF 14.3 / 8.8V 8.4 / 7.2V
Typical Application - 48V Input Dual Output Flyback
CR5 +3.3V T1 VIN+ R3 C4 CR4 C17 + C22 + C20 RETURN CR6 R1 36-75V C6 C1 C3 Q1 U2 C21 R21 +1.8V + C15 + C16
C2 C5
CR2
C19
3
VINR6 Q3 VR1
ISL6842, ISL6843, ISL6844, ISL6845
R16
R17 R19 C14
R18
R4
R22 U3 R27
C13
R15
R20 U4 R26 COMP VREF CS FB V DD OUT
RTCT GND ISL684x
CR1
R10
C12 C8 R13 C11
ISL6842, ISL6843, ISL6844, ISL6845
Absolute Maximum Ratings
Supply Voltage, VDD . . . . . . . . . . . . . . . . . . . GND - 0.3V to +20.0V OUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to VDD + 0.3V Signal Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . GND - 0.3V to 6.0V Peak GATE Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1A ESD Classification Human Body Model (Per MIL-STD-883 Method 3015.7) . . .2000V Charged Device Model (Per EOS/ESD DS5.3, 4/14/93) . . .1000V
Thermal Information
Thermal Resistance (Typical, Note 1) JA (oC/W) SOIC Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 MSOP Package . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130 Maximum Junction Temperature . . . . . . . . . . . . . . . -55oC to 150oC Maximum Storage Temperature Range . . . . . . . . . -65oC to 150oC Maximum Lead Temperature (Soldering 10s) . . . . . . . . . . . . .300oC (SOIC- Lead Tips Only)
Operating Conditions
Temperature Range ISL684xIx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40oC to 105oC Supply Voltage Range (Typical) ISL6843/5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9V-16V ISL6842/4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15V-18V
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device. This is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
NOTES: 1. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details. 2. All voltages are with respect to GND.
Electrical Specifications
Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application schematic. VDD = 15V (Note 6), Rt = 10k, Ct = 3.3nF, TA = -40 to 105oC (Note 3), Typical values are at TA = 25oC TEST CONDITIONS MIN TYP MAX UNITS
PARAMETER UNDERVOLTAGE LOCKOUT START Threshold (ISL6843, ISL6845) START Threshold (ISL6842, ISL6844) STOP Threshold (ISL6843, ISL6845) STOP Threshold (ISL6842, ISL6844) Hysteresis (ISL6843, ISL6845) Hysteresis (ISL6842, ISL6844) Start-Up Current, IDD Operating Current, IDD Operating Supply Current, ID REFERENCE VOLTAGE Overall Accuracy Long Term Stability Fault Voltage VREF Good Voltage Hysteresis Current Limit, Sourcing Current Limit, Sinking CURRENT SENSE Input Bias Current CS Offset Voltage COMP to PWM Comparator Offset Voltage Input Signal, Maximum
7.8 13.3 6.7 8.0 VDD < START Threshold (Note 4) Includes 1nF GATE loading -
8.4 14.3 7.2 8.8 0.8 5.4 60 3.3 4.1
9.0 15.3 7.7 9.6 100 4.0 5.5
V V
V V V A mA mA
Over line (VDD = 12V to 18V), load, temp TA = 125oC, 1000 hours (Note 5)
4.925 4.40 4.60 50 -20 5
5.000 5 4.65 4.80 165 -
5.050 4.85 VREF-0.05 250 -
V mV V V mV mA mA
VCS = 1V VCS = 0V (Note 5) VCS = 0V (Note 5)
-1.0 95 0.80 0.91
100 1.15 0.97
1.0 105 1.30 1.03
A mV V V
4
ISL6842, ISL6843, ISL6844, ISL6845
Electrical Specifications
Recommended operating conditions unless otherwise noted. Refer to Block Diagram and Typical Application schematic. VDD = 15V (Note 6), Rt = 10k, Ct = 3.3nF, TA = -40 to 105oC (Note 3), Typical values are at TA = 25oC (Continued) TEST CONDITIONS 0 < VCS < 910mV, VFB = 0V (Note 5) (Note 5) MIN 2.5 TYP 3.0 25 MAX 3.5 40 UNITS V/V nS
PARAMETER Gain, ACS = VCOMP/VCS CS to OUT Delay ERROR AMPLIFIER Open Loop Voltage Gain Unity Gain Bandwidth Reference Voltage FB Input Bias Current COMP Sink Current COMP Source Current COMP VOH COMP VOL PSRR OSCILLATOR Frequency Accuracy Frequency Variation with VDD Temperature Stability Amplitude, Peak to Peak RTCT Discharge Voltage Discharge Current OUTPUT Gate VOH Gate VOL Peak Output Current Rise Time Fall Time PWM Maximum Duty Cycle
(Note 5) (Note 5) VFB = VCOMP VFB = 0V VCOMP = 1.5V, VFB = 2.7V VCOMP = 1.5V, VFB = 2.3V VFB = 2.3V VFB = 2.7V Frequency = 120Hz, VDD = 12V to 18V (Note 5)
60 3.5 2.475 -1.0 1.0 -0.4 4.80 0.4 60
90 5 2.500 -0.2 80
2.525 1.0 VREF 1.0 -
dB MHz V A mA mA V V dB
Initial, TJ = 25oC T = 25oC (F18V - F12V)/F12V (Note 5)
49 -
52 0.2 1.9 0.7 8.4
55 1.0 5 9.5
kHz % % V V mA
RTCT = 2.0V
7.2
VDD - OUT, IOUT = -200mA OUT - GND, IOUT = 200mA COUT = 1nF (Note 5) COUT = 1nF (Note 5) COUT = 1nF (Note 5)
-
1.0 1.0 1.0 20 20
2.0 2.0 40 40
V V A nS nS
ISL6842, ISL6843 ISL6844, ISL6845
94 47 -
96 48 -
0 0
% % % %
Minimum Duty Cycle
ISL6842, ISL6843 ISL6844, ISL6845
NOTES: 3. Specifications at -40oC are guaranteed by design, not production tested. 4. This is the VDD current consumed when the device is active but not switching. Does not include gate drive current. 5. Guaranteed by design, not 100% tested in production. 6. Adjust VDD above the start threshold and then lower to 15V.
5
ISL6842, ISL6843, ISL6844, ISL6845 Typical Performance Curves
1.02 NORMALIZED FREQUENCY 1.01 1 0.99 0.98 0.97 -40 1.001 1 NORMALIZED VREF -10 20 50 80 110 0.999 0.998 0.997 0.996 0.995 -40 -25 -10 5 20 35 50 65 80 95 110 TEMPERATURE (oC)
TEMPERATURE (oC)
FIGURE 1. FREQUENCY vs TEMPERATURE
FIGURE 2. REFERENCE VOLTAGE vs TEMPERATURE
1.002 NORMALIZED EA REFERENCE
1-103 CT= 100pF 100 220pF 330pF 470pF 1.0nF 10 2.2nF 3.3nF 4.7nF
0.998
0.996
0.994 -40 -25 -10 5 20 35 50 65 80 95 110 1 10 20 30 40 50 60 70 80 90 100 RT (k) TEMPERATURE (oC)
FREQUENCY (kHz)
1
FIGURE 3. EA REFERENCE vs TEMPERATURE
FIGURE 4. RTCT vs FREQUENCY
Pin Descriptions
RTCT - This is the oscillator timing control pin. The operational frequency and maximum duty cycle are set by connecting a resistor, RT, between VREF and this pin and a timing capacitor, CT, from this pin to GND. The oscillator produces a sawtooth waveform with a programmable frequency range up to 2.0MHz. The charge time, TC, the discharge time, TD, the switching frequency, f, and the maximum duty cycle, Dmax, can be calculated from the following equations:
0.583 * RT * CT 0.0083 * RT - 4.3 - RT * CT * ln ---------------------------------------------- 0.0083 * RT - 2.4 (EQ. 1) (EQ. 2)
COMP - COMP is the output of the error amplifier and the input of the PWM comparator. The control loop frequency compensation network is connected between the COMP and FB pins. FB - The output voltage feedback is connected to the inverting input of the error amplifier through this pin. The non-inverting input of the error amplifier is internally tied to a reference voltage. CS - This is the current sense input to the PWM comparator. The range of the input signal is nominally 0 to 1.0V and has an internal offset of 100mV. GND - GND is the power and small signal reference ground for all functions. OUT - This is the drive output to the power switching device. It is a high current output capable of driving the gate of a power MOSFET with peak currents of 1.0A. This GATE output is actively held low when VDD is below the UVLO threshold.
T T
C D
f = 1 (TC + TD)
D = TC * f
(EQ. 3) (EQ. 4)
Figure 4 may be used as a guideline in selecting the capacitor and resistor values required for a given frequency. 6
ISL6842, ISL6843, ISL6844, ISL6845
VDD - VDD is the power connection for the device. The total supply current will depend on the load applied to OUT. Total IDD current is the sum of the operating current and the average output current. Knowing the operating frequency, f, and the MOSFET gate charge, Qg, the average output current can be calculated from:
I OUT = Qg x f (EQ. 5)
damps any oscillations caused by the resonant tank of the parasitic inductances in the traces of the board and the FET's input capacitance.
Slope Compensation
For applications where the maximum duty cycle is less than 50%, slope compensation may be used to improve noise immunity, particularly at lighter loads. The amount of slope compensation required for noise immunity is determined empirically, but is generally about 10% of the full scale current feedback signal. For applications where the duty cycle is greater than 50%, slope compensation is required to prevent instability. The minimum amount of slope compensation required corresponds to 1/2 the inductor downslope. Adding excessive slope compensation, however, results in a control loop that behaves more as a voltage mode controller than as current mode controller.
CS SIGNAL (V) DOWNSLOPE CURRENT SENSE SIGNAL
To optimize noise immunity, bypass VDD to GND with a ceramic capacitor as close to the VDD and GND pins as possible. VREF - The 5.00V reference voltage output. +1.0/-1.5% tolerance over line, load and operating temperature. Bypass to GND with a 0.1F to 3.3F capacitor to filter this output as needed.
Functional Description
Features
The ISL6842, ISL6843, ISL6844, ISL6845 current mode PWMs make an ideal choice for low-cost flyback and forward topology applications. With its greatly improved performance over industry standard parts, it is the obvious choice for new designs or existing designs which require updating.
TIME
Oscillator
The ISL6842, ISL6843, ISL6844, ISL6845 controllers have a sawtooth oscillator with a programmable frequency range to 2MHz, which can be programmed with a resistor from VREF and a capacitor to GND on the RTCT pin. (Please refer to Fig. 4 for the resistor and capacitance required for a given frequency.)
FIGURE 6. CURRENT SENSE DOWNSLOPE
Slope compensation may added to the CS signal in the following manner.
ISL6842, ISL6843, ISL6844, ISL6845
RTCT
Soft Start Operation
Soft start must be implemented externally. One method, illustrated below, clamps the voltage on COMP.
VREF
CS ISL6842, ISL6843, ISL6844, ISL6845
VREF
COMP
FIGURE 7. SLOPE COMPENSATION
GND
Fault Conditions
A Fault condition occurs if VREF falls below 4.65V. When a Fault is detected OUT is disabled. When VREF exceeds 4.80V, the Fault condition clears, and OUT is enabled.
FIGURE 5. SOFT START
Ground Plane Requirements
Careful layout is essential for satisfactory operation of the device. A good ground plane must be employed. A unique section of the ground plane must be designated for high di/dt currents associated with the output stage. VDD should be bypassed directly to GND with good high frequency capacitors.
Gate Drive
The ISL6842, ISL6843, ISL6844, ISL6845 are capable of sourcing and sinking 1A peak current. To limit the peak current through the IC, an optional external resistor may be placed between the totem-pole output of the IC (OUT pin) and the gate of the MOSFET. This small series resistor also 7
ISL6842, ISL6843, ISL6844, ISL6845 Small Outline Plastic Packages (SOIC)
N INDEX AREA E -B1 2 3 SEATING PLANE -AD -CA h x 45o H 0.25(0.010) M BM
M8.15 (JEDEC MS-012-AA ISSUE C)
8 LEAD NARROW BODY SMALL OUTLINE PLASTIC PACKAGE INCHES SYMBOL A
L
MILLIMETERS MIN 1.35 0.10 0.33 0.19 4.80 3.80 MAX 1.75 0.25 0.51 0.25 5.00 4.00 NOTES 9 3 4 5 6 7 8o Rev. 0 12/93
MIN 0.0532 0.0040 0.013 0.0075 0.1890 0.1497
MAX 0.0688 0.0098 0.020 0.0098 0.1968 0.1574
A1 B C D E
A1 0.10(0.004) C
e H h L N
0.050 BSC 0.2284 0.0099 0.016 8 0o 8o 0.2440 0.0196 0.050
1.27 BSC 5.80 0.25 0.40 8 0o 6.20 0.50 1.27
e
B 0.25(0.010) M C AM BS
NOTES: 1. Symbols are defined in the "MO Series Symbol List" in Section 2.2 of Publication Number 95. 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Dimension "D" does not include mold flash, protrusions or gate burrs. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension "E" does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side. 5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area. 6. "L" is the length of terminal for soldering to a substrate. 7. "N" is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. The lead width "B", as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch). 10. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact.
8
ISL6842, ISL6843, ISL6844, ISL6845 Mini Small Outline Plastic Packages (MSOP)
N
M8.118 (JEDEC MO-187AA)
8 LEAD MINI SMALL OUTLINE PLASTIC PACKAGE
E1 E
INCHES SYMBOL MIN 0.037 0.002 0.030 0.010 0.004 0.116 0.116 MAX 0.043 0.006 0.037 0.014 0.008 0.120 0.120
MILLIMETERS MIN 0.94 0.05 0.75 0.25 0.09 2.95 2.95 MAX 1.10 0.15 0.95 0.36 0.20 3.05 3.05 NOTES 9 3 4 6 7 15o 6o Rev. 2 01/03
INDEX AREA
-B12 TOP VIEW 0.25 (0.010) GAUGE PLANE SEATING PLANE -C4X R1 R 0.20 (0.008) ABC
A A1 A2 b c D E1
4X L L1
e E L
0.026 BSC 0.187 0.016 0.199 0.028
0.65 BSC 4.75 0.40 5.05 0.70
A
A2
A1
-He D
b
0.10 (0.004) -A0.20 (0.008)
C
SEATING PLANE
L1 N R
0.037 REF 8 0.003 0.003 5o 0o 15o 6o
0.95 REF 8 0.07 0.07 5o 0o
C a C L E1
C
R1 0
SIDE VIEW
-B-
0.20 (0.008)
CD
END VIEW
NOTES: 1. These package dimensions are within allowable dimensions of JEDEC MO-187BA. 2. Dimensioning and tolerancing per ANSI Y14.5M-1994. 3. Dimension "D" does not include mold flash, protrusions or gate burrs and are measured at Datum Plane. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension "E1" does not include interlead flash or protrusions and are measured at Datum Plane. - H - Interlead flash and protrusions shall not exceed 0.15mm (0.006 inch) per side. 5. Formed leads shall be planar with respect to one another within 0.10mm (0.004) at seating Plane. 6. "L" is the length of terminal for soldering to a substrate. 7. "N" is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. Dimension "b" does not include dambar protrusion. Allowable dambar protrusion shall be 0.08mm (0.003 inch) total in excess of "b" dimension at maximum material condition. Minimum space between protrusion and adjacent lead is 0.07mm (0.0027 inch). 10. Datums -A -H- . and - B - to be determined at Datum plane
11. Controlling dimension: MILLIMETER. Converted inch dimensions are for reference only.
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