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PDF SC4810E Data sheet ( Hoja de datos )
| Número de pieza | SC4810E | |
| Descripción | High Performance Current Mode PWM Controller | |
| Fabricantes | Semtech Corporation | |
| Logotipo |  |
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POWER MANAGEMENT
Description
SC4810B/E
High Performance Current Mode PWM Controller
with Complementary Output, Programmable Delay
Features
The SC4810B/E is a 16 pin BICMOS primary side PWM
controller for use in Isolated DC-DC and off-line switching
power supplies. It is a highly integrated solution, requiring
few external components. It features a high frequency
of operation, accurately programmable maximum duty
cycle, current mode control, line voltage monitoring, supply
UVLO, low start-up current, and programmable soft start
with user accessible reference. It operates in a fixed
www.DatafSrheeqeut4eUn.ccoym, highly desirable for Telecom applications. The
output for switch is complementary to each other with
programmable delay between each transition. The active
technique allows single ended converters beyond 50%
duty cycle and greater flux swing for the power
transformer while reducing voltage stresses on the
switches. The separate sync pin simplifies synchronization
to an external clock. Feeding the oscillator of one device
to the sync of another forces biphase operation which
reduces input ripple and filter size.
The SC4810B/E has a turn-on voltage threshold of 7V.
In the SC4810B, OUT2 is inverted to drive the N-MOSFET.
In the SC4810E, OUT2 is non-inverted to drive the
P-MOSFET. These devices are available in a TSSOP-16 or
MLPQ-16 lead package.
Operation to 1MHz
Accurate programmable maximum duty cycle
Line voltage monitoring
External frequency synchronization
Bi-phase mode of operation for low ripple
Independent programmable delays
Hiccup mode current limit
Under 250µA start-up current
Programmable maximum volt-second clamp
Accessible reference voltage
VDD undervoltage lockout
-40°C to 105°C operating temperature
16 lead TSSOP or MLPQ lead free packages. Both
fully WEEE and RoHS compliant
Applications
Telecom equipment and power supplies
Networking power supplies
Power over LAN applications
Industrial power supplies
Isolated power supplies
VoIP phones
Typical Application Circuit
+48V
R1
C1
D2 Q1
D1
C3
R2
C4
C5
T1
D3
D4
C7
R3 U1 T2
S C 130 2A
R5 C9 R6
C8
U2
2
R7
7
C10
6 RAMP
OUT2 13 4
5
R9
3 SYNC
OUT1 15
R10
4 RCT SC4810
CS 10
R 11
5 DMAX
R12
7 DELAY 1
R 14
C13 8 DELAY 2
Q4
R17 R18 R19
FB 11
VREF 16
SS
9 C12
C 15
C 11
R 20
R22
C6
R4
Q2
D5
Q3
R 13
U3
6
5
1
2
R23 C16
L1
C2
R8
R15
U4
SC 431L
C14
Vout
R16
R21
Revision: July 27, 2006
1
www.semtech.com
1 page  
POWER MANAGEMENT
Pin Configurations
TOP VIEW
VDD
LUVLO
SYNC
RCT
DMAX
www.DataSheet4U.com RAMP
DELAY 1
DELAY 2
1
2
3
4
5
6
7
8
16 VREF
15 OUT1
14 PGND
13 OUT2
12 GND
11 FB
10 CS
9 SS
(16 Pin TSSOP )
TOP VIEW
SC4810B/E
Ordering Information
Part Number(2)
SC4810BITSTRT
SC4810EITSTRT
SC4810BIMLTRT
SC4810EIMLTRT
Package(1)
TSSOP-16
MLPQ-16
Temp. Range (TJ)
-40°C to 105°C
Notes:
(1) Only available in tape and reel packaging. A reel
contains 2500 devices for TSSOP and 3000 parts
for MLP package.
(2) Lead free product. This product is fully WEEE and
RoHS compliant.
(16 Pin MLPQ)
2006 Semtech Corp.
5
www.semtech.com
5 Page 
SC4810B/E
POWER MANAGEMENT
Application Information (Cont.)
output voltage ripple. The designer needs to take the
output inductance and output capacitance and the ESL
and ESR of the output capacitor into consideration during
the design.
For this application, one Panasonic power choke output
inductor was selected and three 6.3V, 100uF TDK
ceramic capacitors were adopted in the design.
www.DataSSheeleetc4Uti.oconmof the Current Sensing Resistor
The selection of the current sensing resistor is based on
the over-current protection triggering point. SC4810
employs a Hiccup mode over-current protection with an
overcurrent threshold of 600mV. A voltage signal above
600mV on the CS pin will trigger hiccup mode overcurrent
protection. Suppose the over-current protection setpoint
is set to be Iov. The threshold voltage of SC4810 is
Vthreshold. The turns ratio of the power transformer is
Ns/Np. The turns ratio of the current sensing transformer
is Ncs:1. Then the Rsense would be calculated as:
Rsense
=
VThreshold × NP × NCS
IOV × NS
......(1)
VRCT
3V
0V
Fig.4 Voltage Waveform on RCT Pin
VPK
t
As illustrated, the capacitor C is charged via the resistor
R from VREF. Whenever the voltage on the RCT pin
reaches 3V, the capacitor C will be discharged through
an internal FET shorted to ground. When the clock signal
circuit is connected as in Fig.3, the frequency of the clock
signal is defined, as in equation 2.
F = 1 ........(2)
−
(RT
+ 1k)
•
CT
•
ln
1 −
VP−K
VREF
VSRCE4F 8is10tAh/eDr
eference voltage of the SC4
and 5V for SC4810B/C/E.
810,
4V
for
In this application, to get 600kHz, C = 180pF,
(R + 1k) = 10k ohms and VP-K = 3V.
Set Clock Frequency
Maximum Duty Ratio Limit
The SC4810 uses a pair of resistors and capacitors to
generate a triangle signal as the clock signal, as illustrated
in Fig. 3.
SC4810 features maximum duty ratio limitation for ex-
tra protection. The maximum duty ratio is determined by
the voltage on DMAX pin. As illustrated as in Fig. 5, VDMAX
will be compared with VRCT and DMAX is determined by
the comparison of the two signals.
VRCT
RCT
CR
VREF
Fig. 3 Configuration for Clock Signal
The voltage waveform on the RCT pin is illustrated as in
Fig. 4.
2006 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet SC4810E.PDF ] | |
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