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PDF R7735 Data sheet ( Hoja de datos )
| Número de pieza | R7735 | |
| Descripción | High Performance PWM Flyback Controller | |
| Fabricantes | Richtek Technology | |
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®
R7735
High Performance PWM Flyback Controller
General Description
R7735 series is the successor of R7732/3 and fully
compatible with most of SOT-23-6 / DIP-8 product so far
in the market. It has enhanced mode PWM controller and
owns excellent green power performance, especially under
light load and no load conditions. It focuses on "easy to
design" in different applications and it will save both design
effort and external components.
Besides the general features shown in the Features
section, R7735 covers wide protection options, such as
internal Over Load Protection (OLP) and Over Voltage
Protection (OVP) to eliminate the external protection
circuits. Moreover, it also features Secondary Rectifier
Short Protection (SRSP) and CS pin open protection. This
protection will make the PSU design for reliability and
safety easier.
R7735 is designed for power supply such as NB adaptor
which is a very cost effective and compact design. The
precise external OVP and Over Temperature Protection
(OTP) can be implemented by very simple circuit. The
start-up resistors can also be replaced by bleeding
resistors to save power loss and component count.
Ordering Information
R7735
(B)* (* : See Version Table)
Package Type
E : SOT-23-6
N : DIP-8 (R7735G Only)
Lead Plating System
G : Green (Halogen Free and Pb Free)
R7735 Version (Refer to Version Table)
Note :
Richtek products are :
RoHS compliant and compatible with the current
requirements of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Features
No Load Input Power Under 100mW
Accurate Over Load Protection
UVLO 9V/14V
Current Mode Control
Slope Compensation
Internal Leading Edge Blanking
Excellent Green Power Performance
Cycle-by-Cycle Current Limit
Internal Over Voltage Protection
Secondary Rectifier Short Protection
Opto-Coupler Short Protection
Feedback Open-Loop Protection
CS Pin Open Protection
Jittering Frequency
PRO Pin for External Arbitrary OVP/OTP
Soft Driving for EMI Noise
High Noise Immunity
RoHS Compliant and Halogen Free
Application
Switching AC/DC Adaptor
DVD Open Frame Power Supply
Set-Top Box (STB)
ATX Standby Power
TV/Monitor Standby Power
PC Peripherals
NB Adaptor
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area.
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
R7735-04 May 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
R7735
Parameter
Symbol
Test Conditions
Min Typ Max Unit
Oscillator Section
Normal PWM Frequency
fOSC
R7735G/R/L/A
R7735H
60 65 70
kHz
92 100 108
Minimum Burst Switching Green
Mode Frequency
fBS_MIN
R7735G/R/L/A
R7735H
18 22 --
kHz
-- 25 --
Maximum Duty Cycle
PWM Frequency Jitter Range
DCYMAX
f
70 75 80 %
-- ±6 -- %
PWM Frequency Jitter Period
Frequency Variation Versus
VDD Deviation
Frequency Variation Versus
Temperature Deviation
TJIT
fDV
fDT
For 65kHz
VDD = 12V to 25V
-- 4 -- ms
-- -- 2 %
TA = 30°C to 105°C (Note 5) -- -- 5 %
COMP Input Section
Open-Loop Voltage
COMP Open-Loop Protection
Delay Time
VCOMP_OP COMP pin Open
R7735G/R/L
TOLP
R7735A
R7735H
5.5 5.75 6
45 56 65
22 28 34
30 36 42
V
ms
Short Circuit Current
Burst Switching Green Mode
Entry Voltage
Burst Switching Green Mode
Ending Voltage
IZERO
VBS_ET
VBS_ED
VCOMP = 0V
R7735G/R/L/A
R7735H
0.15 0.29 0.45 mA
2.85 3 3.15 V
2.75 2.9 3.05
2.65 2.8 2.95
V
Current Sense Section
Initial Peak Current Limitation
Offset
Maximum Clamping Current Limit
Leading Edge Blanking Time
Internal Propagation Delay Time
Minimum On Time
VCS_TH
VCS(MAX)
tLEB
tPD
tON(MIN)
(Note 5)
(Note 6)
(Note 6)
0.68 0.7 0.72
1.05 1.1 1.15
150 250 350
-- 100 --
250 350 450
V
V
ns
ns
ns
GATE Section
Rising Time
Falling Time
GATE Output Clamping Voltage
tR
tF
VCLAMP
VDD = 15V, CL = 1nF
VDD = 15V, CL = 1nF
VDD = 25V
60 125 140
25 40 65
12.1 14 15.9
ns
ns
V
PRO Interface Section
Pull Low Threshold
Pull High Threshold
Internal Bias Current
Pull High Sinking Current
VL_TH
VH_TH
IBIAS
ISINK
(Note 7)
0.47 0.5 0.53 V
3.5 3.8 4.1
V
90 100 110 A
0.7 -- 1.4 mA
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
R7735-04 May 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
R7735
Application Information
Burst Switching Green Mode
During light load, switching loss will dominate the power
efficiency calculation. This mode is to cut switching loss.
When the output load gets light, feedback signal drops
and touches VBURL. PWM signal will be blanked and
system ceases to switch. After VOUT drops and feedback
signal goes back to VBURH, switching will be resumed.
VDD Holdup Mode
Under light load or load transient moment, feedback signal
will drop and touch VBURL. Then PWM signal will be
blanked and system ceases to switch. VDD could drop
down to turn off threshold voltage. To avoid this, when VDD
drops to a setting threshold (Typ. = 10V), the hysteresis
comparator will bypass PWM and burst mode loop and
forces switching at a very low level to supply energy to
VDD pin. VDD holdup mode was also improved to hold up
VDD by less switching cycles. This mode is very useful in
reducing start-up resistor loss while still get start-up time
in spec. It's not likely for VDD to touch UVLO turn off
threshold during any light load condition. This will also
makes bias winding design and transient design easier.
Furthermore, VDD holdup mode is only designed to prevent
VDD from touching turn off threshold voltage under light
load or load transient moment. Relative to burst mode,
switching loss will increase on the system at VDD holdup
mode, so it is highly recommended that the system should
avoid operating at this mode during light load or no load
condition, normally.
Start-up Circuit
To minimize power loss, it's recommended that the start-
up current is from bleeding resistor. It's not only good for
power saving but also could reset latch mode protection
quickly. Figure 1 shows IDD_Avg vs. RBleeding curve. User
can apply this curve to design the adequate bleeding
resistor.
Gate Driver
A totem pole gate driver is fine tuned to meet both EMI
and efficiency requirement in low power application. An
internal pull low circuit is activated after pretty low VDD to
prevent external MOSFET from accidentally turning on
during UVLO.
Oscillator
To guarantee precise frequency, it's trimmed to 5%
tolerance. It also generates slope compensation saw-tooth,
75% maximum duty cycle pulse and overload protection
slope. It can typically operate at built-in 65kHz center
frequency and features frequency jittering function. Its
jittering depth is 6% with about 4ms envelope frequency
at 65kHz.
IDD_Avg vs. RBleeding Curve
30
28
26
24
RBleeding
IDD_Avg
22 RBleeding
20
18
90Vac
16 85Vac
14 80Vac
VDD
12
10
2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0
RBleeding Curve (MΩ)
Figure 1. IDD_Avg vs. RBleeding Curve
Copyright ©2014 Richtek Technology Corporation. All rights reserved.
R7735-04 May 2014
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet R7735.PDF ] | |
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