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Description
GM384XA series is high performance with fixed-frequency current mode PWM controllers. They are specially designed for off-Line and DC-to-DC converter applications. They require minimal external components to precisely tailor performance in a wide variety of applications. GM384XA series includes a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, high gain error amplifier, a current-sensing comparator, and a high-current totem pole output for driving a power MOSFET. On-chip protection features include undervoltage lockouts with hysteresis for both input and reference, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering. All these are in a simple DIP-8 or SOP-8 package! GM3842A and GM3844A have UVLO thresholds of 16V (on)/10V(off); GM3843A and GM3845A have UVLO thresholds of 8.4V (on)/ 7.6V (off). GM3842A and GM3843A operate within 100% duty cycle; GM3844A and GM3845A operate within 50% duty cycle.
Features
Low Start-Up and Operating Current Automatic Feed Forward Compensation Current Mode Operating Frequency up to 500kHz Trimmed Oscillator Discharge Current for Precise Duty Cycle Control Latching PWM for Cycle-By-Cycle Current Limiting Undervoltage Lockout with Hysteresis High Current Totem Pole Output The GM384XA Have Start-up Current 0.17mA
SIMPLIFIED BLOCK DIAGRAM
VCC 7 Vref 8 R R VREF Undervoltage LOCKOUT OSCILLATOR Error Amplifier + Latching PWM 5 Power Ground 3 Current Sense Input 5 GND 5.0V REFERENCE VCC Undervoltage LOCKOUT 7 VC
RT/ CT 4
6 Output
Voltage Feedback Input 2 Output Compensation 1
GM3842A, GM3843A, GM3844A, GM3845A
1
www.gammamicro.com
GM 431
V1.0
MARKING INFORMATION & PIN CONFIGURATIONS (TOP VIEW)
SOP - 8
VCC VREF
8 7 6 5
DIP - 8
OUTPUT GND
VCC VREF
8 7 6 5
GM384X Ayww
OUTPUT GND
GM384X Ayww
1 2 3 4
1 2 3 4
COMP FB
RT / C T ISENSE
COMP FB
RT / C T ISENSE
A = Assembly Location Y = Year W W = Weekly
ORDERING INFORMATION (Green Package Products are available now!)
GM3842A, GM3843A, GM3844A, GM3845A
Ordering Number
GM3842AS8T GM3842AS8R GM3842AD8T GM3843AS8T GM3843AS8R GM3843AD8T GM3844AS8T GM3844AS8R GM3844AD8T GM3845AS8T GM3845AS8R GM3845AD8T
Package
SOP - 8 SOP - 8 DIP-8 SOP - 8 SOP - 8 DIP-8 SOP - 8 SOP - 8 DIP-8 SOP - 8 SOP - 8 DIP-8
Shipping
100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube 100 Units/ Tube 2,500 Units/ Tape & Reel 60 Units/ Tube
* For detail ordering number identification, please see last page. ** For green package products, please add " G" at the end of each part number.
2
ABSOLUTE MAXIMUM RATINGS
PARAMETER
Supply Voltage (low impedance source) Output Current, Source or Sink * Input Voltage (analog inputs pins 2) Maximum Power Dissipation (TA= 25°C) Error Amp Output Sink Current Storage Temperature Range Lead Temperature (soldering 5 sec.)
* Note: Maximum Package Power Dissipation Limits must be observed.
SYMBOL
VCC IO VI PD ISINK(E.A) Tstg TL
VALUE
30 ±1.0 - 0.3 to + 5.5 1.0 10 - 65 to + 150 260
UNIT
V A V W mA °C °C
PACKAGE PIN DESCRIPTION
1 2
COMP VFB ISENSE RT/ CT GND Output VCC VREF
This pin is Error Amplifier output and is made available for loop compensation. This is the inverting input of the Error Amplifier. It is normally connected to the switching power supply output through a resistor divider. A voltage proportional to inductor current connected to this input. The PWM uses this information to terminate the output switch conduction. Oscillator frequency and maximum Output cycle are programmed by connecting resistor RT to VREF and capacitor CT to ground. This pin is the combined control circuitry and power ground. This output directly drives the gate of a power MOSFET. Peak current up to 1.0A are sourced and sunk by this pin. This pin is the positive supply of the control integrated circuit (IC) This is the reference output. It provides charging current for capacitor CT through resistor RT.
3
4 5 6 7 8
GM3842A, GM3843A, GM3844A, GM3845A
3
PIN lead
FUNCTION
FUNCTION
Power Management
REPRESENTATIVE BLOCK DIAGRAM
VCC VIN
VCC 7
8 Vref R 2.5V RT R Internal Baias
Reference Regulator
+ VCC UVLO +
36V
VC 7
+ 3.6V + Vref UVLO
4
Oscillator
(Toggle flip flop used only in GM3844A, GM3845A)
Output 6
Q1
CT + 1/2 Vref 1.0mA
TQ S 2R R 1.0V R Current Sense Comparator 5 GND + PWM Latch 3 Current Sense Input Q Power Ground 5
GM3842A, GM3843A, GM3844A, GM3845A
+ 2 Voltage Feedback Input 1 Output Compensation Error Amplifier
+ + -
=
Sink Only Positive True Logic
RS
TIMING DIAGRAM
Capacitor CT
Latch "Set" Input Output/ Compensation Current Sense Input Latch "Reset" Input
Output Latch RT/ Small CT Small RT/ Latch CT
4
ELECTRICAL CHARACTERISTICS
(TA = 0°C to 70°C, *VCC=15V, CT=3.3nF, RT=10kW, unless otherwise specified )
CHARACTERISTICS
Reference Section Reference Output Voltage Line Regulation Load Regulation Short Circuit Output Current Oscillator Section Oscillation Frequency Frequency Change with Voltage Oscillator Amplitude Error Amplifier Section Input Bias Current Input Voltage Open Loop Voltage Gain Power Supply Rejection Ratio Output Sink Current Output Source Current High Output Voltage Low Output Voltage Current Sense Section Current Sense Input Voltage Gain Maximum Input Signal Supply Voltage Rejection Input Bias Current Output Section Low Output Voltage
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
VREF DVREF DVREF ISC
TJ= 25°C, IREF= 1mA 12V 1mA VCC 25V IREF 20mA TA=25°C TJ= 25°C 12V VCC 25V (Peak to Peak)
4.9
5.0 6.0 6.0 -100
5.1 20 25 -180
V mV mV mA
f Df/ DVCC V(OSC) IBIAS VI(EA) AVOL PSRR ISINK ISOURCE VOH VOL GV VI(MAX) SVR IBIAS 12V
47
52 0.05 1.6
57 1.0
kHz % V
VFB= 3V VPIN1=2.5V 2V 12V VO 4V VCC 25V 2.42 65 60 2 -0.5 5.0
-0.1 2.5 90 70 7 -1.0 6.0 0.8
-2 2.58
µA V dB dB mA mA V
VPIN2=2.7V, VPIN1=1.1V VPIN2=2.3V, VPIN1=5V VPIN2=2.3V, RL=15kW to GND VPIN2=2.7V, RL=15kW to PIN8 (Note 1 and 2) VPIN1=5V (Note 1) VCC 25V (Note 1) VPIN3=3V ISINK= 20mA ISINK= 200mA ISOURCE= 20mA ISOURCE= 200mA TJ= 25°C, CL= 1nF(Note 3) TJ= 25°C, CL= 1nF(Note 3)
1.1
V
2.85 0.9
3.0 1.0 70 -3.0
3.15 1.1
V/ V
dB -10 µA
VOL VOH tR tF
0.08 1.4 13 12 13.5 13 45 35
0.4 2.2
V
High Output Voltage Rise Time Fall Time Undervoltage Lockout Section Start Threshold Minimum Operating Voltage (after tum ON)
V 150 150 nS nS
VTH(ST) VOPR(MIN)
GM3842A, GM3844A GM3843A, GM3845A GM3842A, GM3844A GM3843A, GM3845A
14.5 7.8 8.5 7.0
16.0 8.4 10 7.6
17.5 9.0 11.5 8.2
V
V
GM3842A, GM3843A, GM3844A, GM3845A
5
V
ELECTRICAL CHARACTERISTICS (Continued)
(TA = 0°C to 70°C, *VCC=15V, CT=3.3nF, RT=10kW, unless otherwise specified ) CHARACTERISTICS
PWM Section Maximum Duty Cycle Minimum Duty Cycle Total Standby Current Start-Up Current Operating Supply Current Zener Voltage IST ICC(OPR) VZ GM3842A/ 43A/ 44A/ 45A VPIN3= VPIN2=0V ICC= 25mA 30 0.17 13 38 0.3 17 mA mA V D(MAX) D(MIN) GM3842A, GM3843A GM3844A, GM3845A 95 47 97 48 100 50 0 % % %
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
UNIT
* Adjust VCC above the Startup threshold before setting to 15 V. Note1: Parameter measured at trip point of latch with VPIN2 = 0. Note2: Gain defined as A=DVPIN1 / DVPIN3 ; 0 VPIN3 0.8V
Note3: These parameters, although guaranteed, are not 100% tested in production
GM3842A, GM3843A, GM3844A, GM3845A
TYPICAL PERFORMANCE CHARACTERISTICS
RT (KW)
50 CT= 1000pF CT= 200pF 20 10 CT= 2nF 5 CT= 5nF CT= 10pF 2 VCC= 15V 1 TA=25°C 10 20 30 50 100 200 300 500 CT= 1nF CT= 500pF
%
50 30 20 10
VCC= 15V TA=25°C
CT= 5nF CT= 10pF CT= 2nF CT= 1nF CT= 500pF CT= 200pF CT= 1000pF
5 3 2 1
fosc (kHz)
10
20
30
50
100
200 300 500
fosc (kHz)
Figure 1. Timing Resistor vs. Oscillator Frequency
Figure 2. Output Dead-Time vs. Oscillator Frequency
6
TYPICAL PERFORMANCE CHARACTERISTICS
Dmax (%) 90 80 70 60 50 40
VCC= 15V CT= 3.3nF TA=25°C
(dB)
80 60 40 20 0 -20 10
VCC= 15V VO= 2V to 4V RL= 100K TA= 25°C
1
2
3
5
RT (kW)
100
1k
10k
100k
1M
f (Hz)
Figure 3. Maximum Output Duty Cycle vs. Timing Resistor (GM3842A/43A)
Figure 4. Error Amp Open-Loop Gain vs. Frequency
Vth (V) VCC= 15V
1.0 0.8 0.6 0.4 0.2 TA= 125°C TA= 25°C
ISC (mA)
100 90 80 70 60 VCC= 15V
0
2
4
6
VO (V)
50
0
25
50
75
Figure 5. Current Sense Input Threshold vs. Error Amp Output Voltage
100 T (°C) A
Figure 6. Reference Short Circuit Current vs. Temperature
Vsat (V)
-1 -2
80µs Pulsed Load 120Hz Rate
ICC (mA) ISense= 0V
Sourse Saturation (Load to Ground) VFB= 0V RT= 10K TA= 25°C 20 C = 3.3nF T GM3843A/ 45A 15 10 Sink Saturation (Load to VCC) 5 0 200 400 600 IO (mA) 0 10 20 30 VCC(V) Figure 7. Output Saturation Voltage vs. Load Current TA= 25°C Figure 8. Supply Current vs. Supply Voltage
VCC= 15V
3 2 1 0 0
GM3842A, GM3843A, GM3844A, GM3845A
7
GM3842A/ 44A
OPERATING DESCRIPTION
GM3842A, GM3843A, GM3844A and GM3845A are high performance with fixed frequency, current mode controllers. They are designed for off-ine and DC-to-DC converter applications offering great versatility with minimal external components. A representative block diagram is shown on page 4.
Oscillator
The oscillator frequency is determined by the values of the timing components RT and CT. Capacitor CT is charged from the 5.0 V reference through resistor RT to approximately 2.8 V and discharged to 1.2 V by an internal current sink. During the of CT, the oscillator generates an internal blanking pulse that holds the center input of the NOR gate high. This causes the output to be in a low state, thus producing a controlled amount of Figure 2 show RT versus oscillator frequency and Figure 2, Output deadtime versus frequency, both for given values of CT output deadtime. Note that different values of RT and CT will give the same oscillator frequency, but only one combination will yield a specific output deadtime at a given frequency. Th
