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PDF TS3843B Data sheet ( Hoja de datos )
| Número de pieza | TS3843B | |
| Descripción | (TS3842B / TS3843B) High Performance Current Mode Controller | |
| Fabricantes | Taiwan Semiconductor Company | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de TS3843B (archivo pdf) en la parte inferior de esta página. Total 20 Páginas | ||
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TS3842B/3843B
High Performance Current Mode Controller
Designed for Off-Line and DC-to-DC
converter applications.
DIP-8
SOP-8
General Description
The TS3842B and TS3843B series are high performance fixed frequency current mode controllers.
This is specifically designed for Off-Line and DC-to-DC converter applications offering the designer a
www.DatacSohseet te4fUfe.ccotmive solution with minimal external components. This integrated circuits feature a trimmed
oscillator for precise duty cycle control, a temperature compensated reference, high gain error
amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving
a power MOSFET.
Also included are protective features consisting of input and reference undervoltage lockouts each
with hysteresis, cycle-by-cycle current limiting, programmable output deadtime, and a latch for
single pulse metering.
This device is available in 8-pin dual-in-line plastic packages as well as the 8-pin plastic surface
mount (SOP-8). The SOP-8 package has separate power and ground pins for the totem pole output
stage.
The TS3842B has UVLO thresholds of 16V (on) and 10V (off), ideally suited for off-line converters.
Features
Trimmed Oscillator Discharge Current for
Precise Duty Cycle Control
Current Mode Operation to 500KHz
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 Hystersis
Low Start-Up and Operating Current
Block Diagram
VCC 7(12)
Vref
8(14)
RT/CT
4(7)
Voltage
Feedback
Input
2(3)
Output
Compensation
1(1)
R
5.0V
Reference
VCC
Undervoltage
Lockout
Vref
R Undervoltage
Lockout
Oscillator
+
-
Error
Amplifier
Latching
PWM
VC
7(11)
Output
6(10)
Power
Ground
5(8)
Current
Sense
3(5)Input
The document contains information on a new product.Specifications and
information herein are subject to change without notice.
Ordering Information
DEVICE
TS3842/3843BCD
TS3842/3843BCS
OPERATING TEMPERATURE
(Ambient)
-20 to +85+
PACKAGE
DIP-8
SOP-8
1 page  
Electrical Characteristics
VCC=15V (Note 2), RT=10K, CT=3.3nF, TA=Tlow to Thigh (Note 3), unless otherwise noted.
CHARACTERISTIC
OUTPUT SECTION
Output Voltage
Low State (Isink=20mA)
(Isink=200mA)
www.DataSHhieghetS4tUat.ec(oIsmource=20mA)
(Isource=200mA)
Output Voltage with UVLO Activated
VCC=6.0V,Isink=1.0mA
Output Voltage Rise Time (CL=1.0nF,TJ=25+)
Output Voltage Fall Time (CL=1.0nF,TJ=25+)
UNDERVOLTAGE LOCKOUT SECTION
Start-Up Threshold
TS3842B
TS3843B
Minimum Operating Voltage After Turn-On
TS3842B
TS3843B
PWM SECTION
Duty Cycle
Maximum
Minimum
TOTAL DEVICE
Power Supply Current
Start-Up, VCC= 14V
Operating (Note 2)
Power Supply Zener Voltage (ICC=25mA)
SYMBOL
VOL
VOH
VOL(UVLO)
tr
tf
Vth
VCC(min)
DCmax
DCmin
ICC
Vz
MIN
TYP
MAX
UNIT
- 0.1 0.4
- 1.6 2.2
13 13.5
-
12 13.4
-
V
- 0.1 1.1 V
- 50 150 ns
- 50 150 ns
14.5 16 17.5
7.8 8.4 9.0
8.5 10 11.5
7.0 7.6 8.2
V
V
94 96 - %
- -0
-
0.25 0.5
mA
- 12 17
30 36
-
V
Note: 1. Maximum package power dissipation limits must be observed.
2. Adjust VCC above the Start-Up threshold before setting to 15V.
3. Low duty cycle pulse technique are used during test to maintain junction temperature as close to ambient as possible.
Tlow = -20+ ,Thigh = +85+
4. This parameter is measured at the latch trip point with VFB = 0V.
V Output Compensation
5. Comparator gain is defined as : Av =
V Current Sense Input
5 Page 
Undervoltage Lockout(contd.)
This provides a low impedance path for filtering the high frequency noised. All high current loops
should be kept as short as possible using heavy copper runs to minimize radiated EMI. The Error
Amp compensation circuitry and the converter output voltage divider should be located close to
the IC and as far as possible from the power switch and other noise generating components.
www.DataSheet4U.com
Figure 19 - Continuous Current Waveforms
(A)
∆1
Control Voltage
Inductor
Current
m1 m2
∆ 1 + ∆1mm21
Oscillator Period
∆ 1 + ∆1mm21
m2
m1
t0 t1 t2
t3
Control Voltage
(B)
m3
m1
m2
Oscillator Period
Inductor
Current
t4 t5 t6
Current mode converters can exhibit subharmonic oscillations when operating at a duty cycle
greater than 50% with continuous inductor current. This instability is independent of the regula-
tors closed loop characteristics and is caused by the simultaneous operating conditions of fixed
frequency and peak current detecting. Figure 19(A) shows the phenomenon graphically. At t ,
0
switch conduction begins causing the inductor current to rise at a slope of m1. This slope is a
function of the input voltage divided by the inductance. At t1, the Current Sense Input reaches the
threshold established by the control voltage. This causes the switch to turn off and the current to
decay at a slope of m2, until the next oscillator cycle. This unstable condition can be shown if a
perturbation is added to the control voltage, resulting in a small 1(dashed line). With a fixed
oscillator period, the current decay time is reduced, and the minimum current at switch turn-on(t2)
is increased by 1+ 1m2/m1. The minimum current at the next cycle (t3) decreases to ( 1+
1m /m )(m /m ). This perturbation is multiplied by m /m on each succeeding cycle, alternately
21 21
21
increasing and decreasing the inductor current at switch turn-on. Several oscillator cycles may be
required before the inductor current reaches zero causing the process to commence again. If m2/
m is greater than 1, the converter will be unstable. Figure 19(B) shows that by adding an artificial
1
ramp that is synchronized with the PWM clock to the control voltage, the 1 perturbation will
decrease to zero on succeeding cycles. This compensating ramp (m3) must have a slope equal to
or slightly greater than m2/2 for stability. With m2/2 slope compensation, the average inductor
current follows the control voltage yielding true current mode operation. The compensating ramp
can be derived from the oscillator and added to either the Voltage Feedback or Current Sense
inputs (Figure 32).
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet TS3843B.PDF ] | |
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