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UC3844BNG
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Datasheet UC3844BNG Datasheet

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UC3844B, UC3845B, UC2844B, UC2845B
High Performance Current Mode Controllers
Also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle−by−cycle current limiting, a latch for single pulse metering, and a flip−flop which blanks the output off every other oscillator cycle, allowing output deadtimes to be programmed from 50% to 70%.
These devices are available in an 8−pin dual−in−line and surface mount (SOIC−8) plastic package as well as the 14−pin plastic surface mount (SOIC−14). The SOIC−14 package has separate power and ground pins for the totem pole output stage.
The UCX844B has UVLO thresholds of 16V (on) and 10V (off), ideally suited for off−line converters. The UCX845B is tailored for lower voltage applications having UVLO thresholds of 8.5V (on) and 7.6V (off).
Features
• Trimmed Oscillator for Precise Frequency Control
• Oscillator Frequency Guaranteed at 250 kHz
• Current Mode Operation to 500 kHz Output Switching Frequency
• Output Deadtime Adjustable from 50% to 70%
• Automatic Feed Forward Compensation
• Latching PWM for Cycle−By−Cycle Current Limiting
• Internally Trimmed Reference with Undervoltage Lockout
• High Current Totem Pole Output
• Undervoltage Lockout with Hysteresis
• Low Startup and Operating Current
• These Devices are Pb−Free and are RoHS Compliant
• NCV Prefix for Automotive and Other Applications Requiring
Unique Site and Control Change Requirements; AEC−Q100 Qualified and PPAP Capable
V
ref
RT/C
Voltage
Feedback
Input
Output/
Compensation
8(14)
T
4(7)
2(3)
1(1)
R
Undervoltage
R
Lockout
Oscillator
Error
Amplifier
Pin numbers in parenthesis are for the D suffix SOIC-14 package.
GND
Figure 1. Simplified Block Diagram
5.0V
Reference
V
ref
Latching
PWM
5(9)
V
7(12)
CC
V
CC
Undervoltage
Lockout
V
C
7(11)
Output
6(10)
Power Ground
5(8)
Current Sense Input
3(5)
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PDIP−8
N SUFFIX
8
CASE 626
1
SOIC−14
14
1
D SUFFIX
CASE 751A
SOIC−8
8
1
D1 SUFFIX
CASE 751
PIN CONNECTIONS
(Top View)
(Top View)
8
V
ref
7
V
CC
6
Output
5
GN D
14
V
ref
13
NC
12
V
CC
11
V
C
10
Output
9
GND
8
Power Ground
Compensation
Voltage Feedback
Current Sense
RT/C
Compensation
NC
Voltage Feedback
NC
Current Sense
NC
R
T/CT
1
2
3
4
T
1
2
3
4
5
6
7
ORDERING INFORMATION
See detailed ordering and shipping information in the package dimensions section on page 15 of this data sheet.
DEVICE MARKING INFORMATION
See general marking information in the device marking section on page 16 of this data sheet.
© Semiconductor Components Industries, LLC, 2013
August, 2013 − Rev. 11
1 Publication Order Number:
UC3844B/D
UC3844B, UC3845B, UC2844B, UC2845B
MAXIMUM RATINGS
Rating Symbol Value Unit
Bias and Driver Voltages (Zero Series Impedance, see also Total Device spec) (Note 1) VCC, V
C
Total Power Supply and Zener Current (ICC + IZ) 30 mA
Output Current, Source or Sink (Note 2) I
O
Output Energy (Capacitive Load per Cycle) W 5.0
Current Sense and Voltage Feedback Inputs V
Error Amp Output Sink Current I
in
O
Power Dissipation and Thermal Characteristics D Suffix, Plastic Package, SOIC−14 Case 751A
Maximum Power Dissipation @ T
= 25°C
A
Thermal Resistance, Junction−to−Air
P
D
R
q
JA
D1 Suffix, Plastic Package, SOIC−8 Case 751
Maximum Power Dissipation @ T Thermal Resistance, Junction−to−Air
N Suffix, Plastic Package, Case 626
Maximum Power Dissipation @ T Thermal Resistance, Junction−to−Air
Operating Junction Temperature T
Operating Ambient Temperature UC3844B, UC3845B
= 25°C
A
= 25°C
A
P
D
R
q
JA
P
D
R
q
JA
J
T
A
UC2844B, UC2845B
UC3844BV, UC3845BV
Storage Temperature Range T
stg
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect device reliability.
1. The voltage is clamped by a zener diode (see page 9 Under Voltage Lockout section). Therefore this voltage may be exceeded as long as
the total power supply and zener current is not exceeded.
2. Maximum package power dissipation limits must be observed.
3. This device series contains ESD protection and exceeds the following tests: Human Body Model 4000 V per JEDEC Standard
JESD22-A114B, Machine Model Method 200 V per JEDEC Standard JESD22-A115-A
4. This device contains latch-up protection and exceeds 100 mA per JEDEC Standard JESD78
ELECTRICAL CHARACTERISTICS (V
is the operating ambient temperature range that applies [Note 6], unless otherwise noted.)
T
A
= 15 V [Note 5], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max values
CC
UC284xB UC384xB, xBV, NCV384xBV
Characteristic Symbol Min Ty p Max Min Typ Max Unit
REFERENCE SECTION
Reference Output Voltage (I
= 1.0 mA, TJ = 25°C) V
O
Line Regulation (VCC = 12 V to 25 V) Reg
Load Regulation (IO = 1.0 mA to 20 mA) Reg
Temperature Stability T
Total Output Variation over Line, Load, & Temperature V
Output Noise Voltage (f = 10 Hz to 10 kHz, TJ = 25°C) V
ref
S
ref
n
4.95 5.0 5.05 4.9 5.0 5.1 V
line
load
− 2.0 20 − 2.0 20 mV
− 3.0 25 − 3.0 25 mV
− 0.2 − − 0.2 − mV/°C
4.9 − 5.1 4.82 − 5.18 V
− 50 − − 50 −
Long Term Stability (TA = 125°C for 1000 Hours) S − 5.0 − − 5.0 − mV
Output Short Circuit Current I
SC
− 30 − 85 −180 − 30 − 85 −180 mA
OSCILLATOR SECTION
A
= T
low
= 25°C
J
to T
high
Frequency T
T
TJ = 25°C (RT = 6.2 k, CT = 1.0 nF)
Frequency Change with Voltage (VCC = 12 V to 25 V)
Frequency Change w/ Temperature (TA = T
low
to T
high
Oscillator Voltage Swing (Peak−to−Peak) V
f
OSC
Df
OSC
)
Df
OSC
OSC
/DV
/DT
49 48
225
52
−
250
55 56
275
49 48
225
− 0.2 1.0 − 0.2 1.0 %
− 1.0 − − 0.5 − %
− 1.6 − − 1.6 − V
5. Adjust VCC above the Startup threshold before setting to 15 V.
6. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible.
=0°C for UC3844B, UC3845B T
T
low
= − 25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B
=+70°C for UC3844B, UC3845B
high
= − 40°C for UC384xBV, NCV384xBV =+105°C for UC3844BV, UC3845BV
= +125°C for NCV384xBV
36 V
1.0 A
− 0.3 to + 5.5 V
10 mA
862 145
°C/W
702 178
°C/W
1.25 100
°C/W
+150 °C
0 to +70
−25 to +85
−40 to +105
− 65 to +150 °C
52
−
250
55 56
275
mJ
mW
mW
W
°C
mV
kHz
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UC3844B, UC3845B, UC2844B, UC2845B
ELECTRICAL CHARACTERISTICS (V
is the operating ambient temperature range that applies [Note 8], unless otherwise noted.)
T
A
= 15 V [Note 7], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max values
CC
UC284xB UC384xB, xBV,
NCV384xBV
Characteristic Symbol Min Typ Max Min Typ Max Unit
OSCILLATOR SECTION
Discharge Current (V
= 2.0 V) TJ = 25°C
OSC
= T
T
to T
A
low
(UC284XB, UC384XB)
high
(UC384XBV)
I
dischg
7.8
7.5
8.3
−
8.8
7.8
−
8.3
8.8
−
7.6
−
7.2
8.8
−
8.8
−
8.8
ERROR AMPLIFIER SECTION
Voltage Feedback Input (VO = 2.5 V) V
Input Bias Current (VFB = 5.0 V) I
Open Loop Voltage Gain (VO = 2.0 V to 4.0 V) A
FB
IB
VOL
2.45 2.5 2.55 2.42 2.5 2.58 V
− − 0.1 −1.0 − − 0.1 − 2.0
65 90 − 65 90 − dB
Unity Gain Bandwidth (TJ = 25°C) BW 0.7 1.0 − 0.7 1.0 − MHz
Power Supply Rejection Ratio (VCC = 12 V to 25 V) PSRR 60 70 − 60 70 − dB
Output Current − Sink (VO = 1.1 V, VFB = 2.7 V)
Output Current − Source (V
= 5.0 V, VFB = 2.3 V)
O
I
Sink
I
Source
2.0
− 0.512−1.0−−
2.0
− 0.512−1.0−−
Output Voltage Swing
High State (R Low State (R
= 15 k to ground, VFB = 2.3 V)
L
= 15 k to V
L
(UC284XB, UC384XB) (UC384XBV)
, VFB = 2.7 V)
ref
V
OH
V
OL
5.0
6.2
−
0.8
−
−
5.0
6.2
1.1
−
−
−
0.8
−
0.8
−
1.1
1.2
CURRENT SENSE SECTION
Current Sense Input Voltage Gain (Notes 9 & 10)
(UC284XB, UC384XB) (UC384XBV)
Maximum Current Sense Input Threshold (Note 9)
(UC284XB, UC384XB) (UC384XBV)
A
V
2.85−3.0−3.15−2.85
2.85
V
th
0.9−1.0−1.1−0.9
0.85
3.0
3.0
1.0
1.0
3.15
3.25
1.1
1.1
Power Supply Rejection Ratio (VCC = 12 V to 25 V) (Note 9) PSRR − 70 − − 70 − dB
Input Bias Current I
Propagation Delay (Current Sense Input to Output) t
PLH(In/Out)
IB
− − 2.0 −10 − − 2.0 −10
− 150 300 − 150 300 ns
OUTPUT SECTION
Output Voltage
Low State (I
High State (I
Output Voltage with UVLO Activated (VCC = 6.0 V, I
= 20 mA)
Sink
= 200 mA, UC284XB, UC384XB)
(I
Sink
= 200 mA, UC384XBV)
(I
Sink
= 20 mA, UC284XB, UC384XB)
Source
= 20 mA, UC384XBV)
(I
Source
= 200 mA)
(I
Source
= 1.0 mA) V
Sink
Output Voltage Rise Time (CL = 1.0 nF, TJ = 25°C) t
Output Voltage Fall Time (CL = 1.0 nF, TJ = 25°C) t
V
OL
V
OH
OL(UVLO)
r
f
−
13
12
0.1
−
1.6
−
13.5
−
13.4
0.4
2.2
−
−
−
−
−
−
−
−
−
13
12.9 12
0.1
1.6
1.6
13.5
−
13.4
0.4
2.2
2.3
−
−
−
− 0.1 1.1 − 0.1 1.1 V
− 50 150 − 50 150 ns
− 50 150 − 50 150 ns
UNDERVOLTAGE LOCKOUT SECTION
Startup Threshold UCX844B, BV
UCX845B, BV
Minimum Operating Voltage After Turn−On UCX844B, BV
UCX845B, BV
V
V
CC(min)
th
15
7.8168.4179.0
9.0
7.0107.6118.2
14.5
7.8168.4
8.5
7.0107.6
17.5
9.0
11.5
8.2
7. Adjust VCC above the Startup threshold before setting to 15 V.
8. Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. =0°C for UC3844B, UC3845B T
T
low
= − 25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B
=+70°C for UC3844B, UC3845B
high
= − 40°C for UC384xBV, NCV384xBV = +105°C for UC3844BV, UC3845BV
= +125°C for NCV384xBV
9. This parameter is measured at the latch trip point with V
DV Output/Compensation
10.Comparator gain is defined as: A
=
V
DV Current Sense Input
FB
= 0 V.
mA
mA
mA
V
V/V
V
mA
V
V
V
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UC3844B, UC3845B, UC2844B, UC2845B
ELECTRICAL CHARACTERISTICS (V
values T
is the operating ambient temperature range that applies [Note 12], unless otherwise noted.)
A
= 15 V [Note 11], RT = 10 k, CT = 3.3 nF. For typical values TA = 25°C, for min/max
CC
UC284xB UC384xB, xBV, NCV384xBV
Characteristic Symbol Min Typ Max Min Typ Max Unit
PWM SECTION
Duty Cycle
Maximum (UC284XB, UC384XB)
Maximum (UC384XBV)
Minimum
DC
DC
(max)
(min)
47
48
−
−
50
−
−
−
0
47 46
48 48
−
−
TOTAL DEVICE
Power Supply Current
Startup (V
Startup (V
= 6.5 V for UCX845B,
CC
= 14 V for UCX844B, BV)
CC
Operating (Note 11)
Power Supply Zener Voltage (ICC = 25 mA) V
I
CC
Z
−
−
0.3120.5
17
−
−
0.3
12
30 36 − 30 36 − V
11.Adjust VCC above the Startup threshold before setting to 15 V.
12.Low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. =0°C for UC3844B, UC3845B T
T
low
= − 25°C for UC2844B, UC2845B = + 85°C for UC2844B, UC2845B
=+70°C for UC3844B, UC3845B
high
= − 40°C for UC384xBV, NCV384xBV = +105°C for UC3844BV, UC3845BV
=+125°C for NCV384xBV
80
50
Ω
20
8.0
5.0
, TIMING RESISTOR (k )
T
R
2.0 NOTE: Output switches at 1/2 the oscillator frequency
0.8
, OSCILLATOR FREQUENCY (kHz)
f
OSC
For RTu 5KfX
1.72
R
TCT
Figure 2. Timing Resistor
versus Oscillator Frequency
VCC = 15 V T
= 25°C
A
1.0 M500 k200 k100 k50 k20 k10 k
75
1.CT = 10 nF
2.C
70
3.C
4.C
5.C
65
6.C
7.CT = 100 pF
60
55
% DT, PERCENT OUTPUT DEADTIME
50
= 5.0 nF
T
= 2.0 nF
T
= 1.0 nF
T
= 500 pF
T
= 200 pF
T
20 k 50 k 200 k 500 k
, OSCILLATOR FREQUENCY (kHz)
f
OSC
Figure 3. Output Deadtime
versus Oscillator Frequency
50
%
50
0
mA
0.5
17
3
2
4
1
7
5
6
1.0 M100 k10 k
2.55 V
2.5 V
2.45 V
VCC = 15 V A
= -1.0
V
TA = 25°C
0.5 ms/DIV
Figure 4. Error Amp Small Signal
Transient Response
3.0 V
2.5 V
20 mV/DIV
2.0 V
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VCC = 15 V A T
A
1.0 ms/DIV
Figure 5. Error Amp Large Signal
Transient Response
= -1.0
V
= 25°C
200 mV/DIV
100
)
80
60
40
20
, OPEN LOOP VOLTAGE GAIN (dB)
0
VOL
A
-20
Figure 6. Error Amp Open Loop Gain and
UC3844B, UC3845B, UC2844B, UC2845B
VCC = 15 V V
= 2.0 V to 4.0 V
O
R
= 100 k
Gain
100 1.0 k 10 k 100 k 1.0 M
f, FREQUENCY (Hz)
Phase versus Frequency
L
T
A
= 25°C
Phase
0
1.2 VCC = 15 V
30
60
1.0
0.8
TA = 25°C
90
120
0.6
0.4
TA = 125°C
TA = -55°C
, EXCESS PHASE (DEGREES)
150
180
10 M10
0.2
φ
, CURRENT SENSE INPUT THRESHOLD (V
th
0
V
0
2.0 4.0 6.0 8.0 , ERROR AMP OUTPUT VOLTAGE (VO)
V
O
Figure 7. Current Sense Input Threshold
versus Error Amp Output Voltage
0
-4.0
-8.0
-12
-16
-20
, REFERENCE VOLTAGE CHANGE (mV)
ref
V
Δ
-24 0
Figure 8. Reference Voltage Change
VCC = 15 V
TA = -55°C
TA = 125°C
TA = 25°C
20 40 60 80 100 120
I
, REFERENCE SOURCE CURRENT (mA)
ref
versus Source Current
VCC = 15 V I
= 1.0 mA to 20 mA
O
T
= 25°C
A
110
, REFERENCE SHORT CIRCUIT CURRENT (mA)
SC
I
90
70
50
-55
-25 0 25 50 75 100 125 , AMBIENT TEMPERATURE (°C)
T
A
Figure 9. Reference Short Circuit Current
versus Temperature
VCC = 15 V
≤ 0.1 W
R
L
VCC = 12 V to 25 V T
= 25°C
A
O
V Δ , OUTPUT VOLTAGE CHANGE (2.0 mV/DIV)
Figure 10. Reference Load Regulation Figure 11. Reference Line Regulation
2.0 ms/DIV
O
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V Δ , OUTPUT VOLTAGE CHANGE (2.0 mV/DIV)
2.0 ms/DIV
O
S
O
O
G
(
V
)
E
LTA
N V
ATURATI
UTPUT ,
sat
V
-1.0
-2.0
3.0
2.0
1.0
UC3844B, UC3845B, UC2844B, UC2845B
0
V
CC
TA = 25°C
TA = -55°C
0
200 400 600
Source Saturation
(Load to Ground)
TA = -55°C
Sink Saturation
(Load to V
, OUTPUT LOAD CURRENT (mA)
I
O
)
CC
VCC = 15 V 80 ms Pulsed Load 120 Hz Rate
TA = 25°C
GND
VCC = 15 V C
= 1.0 nF
90
%
L
T
= 25°C
A
10
%
8000
50 ns/DIV
Figure 12. Output Saturation Voltage
Figure 13. Output Waveform
versus Load Current
25
20
15
10
, SUPPLY CURRENT (mA)
CC
I
RT = 10 k CT = 3.3 nF V
5
0
0
UCX845B
UCX844B
10 20 30 40
V
, SUPPLY VOLTAGE (V)
CC
I
Sense
T
A
FB
= 0 V
= 0 V
= 25°C
, OUTPUT VOLTAGEV
O
, SUPPLY CURRENT
CC
I
100 ns/DIV
VCC = 30 V C
= 15 pF
L
T
= 25°C
A
100 mA/DIV 20 V/DIV
Figure 14. Output Cross Conduction Figure 15. Supply Current versus Supply Voltage
PIN FUNCTION DESCRIPTION
Pin
8−Pin 14−Pin
1 1 Compensation This pin is the Error Amplifier output and is made available for loop compensation.
2 3 Voltage
3 5 Current Sense A voltage proportional to inductor current is connected to this input. The PWM uses this
4 7 RT/C
5 GND This pin is the combined control circuitry and power ground.
6 10 Output This output directly drives the gate of a power MOSFET. Peak currents up to 1.0 A are sourced
7 12 V
8 14 V
8 Power
11 V
9 GND This pin is the control circuitry ground return and is connected back to the powersource ground.
2,4,6,13 NC No connection. These pins are not internally connected.
Function Description
This is the inverting input of the Error Amplifier. It is normally connected to the switching power
Feedback
supply output through a resistor divider.
information to terminate the output switch conduction.
T
The Oscillator frequency and maximum Output duty cycle are programmed by connecting resistor RT to V
and capacitor CT to ground. Oscillator operation to 1.0 kHz is possible.
ref
and sunk by this pin. The output switches at one−half the oscillator frequency.
CC
ref
This pin is the positive supply of the control IC.
This is the reference output. It provides charging current for capacitor CT through resistor RT.
This pin is a separate power ground return that is connected back to the power source. It is used
Ground
C
to reduce the effects of switching transient noise on the control circuitry.
The Output high state (VOH) is set by the voltage applied to this pin. With a separate power source connection, it can reduce the effects of switching transient noise on the control circuitry.
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