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PDF AP3785T Data sheet ( Hoja de datos )
| Número de pieza | AP3785T | |
| Descripción | PRIMARY SIDE REGULATED SWITCHING MODE POWER SUPPLY CONTROLLER | |
| Fabricantes | Diodes | |
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AP3785T
PRIMARY SIDE REGULATED SWITCHING MODE POWER SUPPLY CONTROLLER
Description
The AP3785T is a high performance AC/DC power supply controller
for battery charger and adapter applications. It can meet less than
10mW standby power for “Super Star” charger criteria. The device
uses Pulse Frequency Modulation (PFM) method to build
discontinuous conduction mode (DCM) flyback power supplies.
The AP3785T provides accurate constant voltage (CV), constant
current (CC) and outstanding dynamic performance without requiring
an opto-coupler. It also eliminates the need of loop compensation
circuitry while maintaining stability.
The AP3785T is equipped with both cable drop compensation
function to meet various cables with different lengths and gauges and
adjustable line voltage compensation function.
Pin Assignments
(Top View)
CS 1
EM 2
VCC 3
OUT 4
SO-8
8 FB
7 CBC
6 OTP
5 GND
When AP3785T is used with AP4341 or synchronous rectifier series
(for example APR343 + MOSFET, APR3415, APR34330), better
under-shoot performance and higher conversion efficiency can be
achieved.
The AP3785T has internal over temperature protection for itself, and
also provides dedicated pin for external over temperature protection.
This IC is available in SO-8 package.
Applications
Adapter/Chargers for Shaver, Cell/Cordless Phones, PDAs, MP3
and Other Portable Apparatus
Standby and Auxiliary Power Supplies
Features
Primary Side Control for Eliminating Opto-coupler
10mW No-load Input Power
Flyback Topology in DCM Operation
External Adjustable Line Compensation for CC
External Adjustable Cable Compensation for CV
Multiple PWM/PFM Control Mode to Improve Audio Noise and
Efficiency
VCS Jitter to Reduce System EMI
Valley-on for the Higher Efficiency and Better EMI
Multiple Protections:
Over Voltage Protection (OVP)
Output Short Circuit Protection (SCP)
Transformer Saturation Protection (TSP) via Primary Peak
Current Limitation
OTP and External Over Temperature Protection (OTP)
Matching AP4341 with Schottky or APR343/APR3415
Synchronous Rectifier Solution
SO-8 Package
Totally Lead-free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Notes:
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
AP3785T
Document number: DS37552 Rev. 4 - 2
1 of 18
www.diodes.com
September 2015
© Diodes Incorporated
1 page  
AP3785T
Absolute Maximum Ratings (Note 5)
Symbol
VCC
–
–
VFB
TJ
TSTG
TLEAD
θJC
θJA
–
–
Parameter
Voltage at VCC to GND
Voltage at OUT, EM to GND
Voltage at CS, CBC,OTP to GND
FB Input Voltage
Operating Junction Temperature
Storage Temperature
Lead Temperature (Soldering, 10 sec)
Thermal Resistance (Junction to Case)
Thermal Resistance (Junction to Ambient)
(Note 6)
ESD (Human Body Model)
ESD (Machine Model)
Rating
-0.3 to 30
-0.3 to 22
-0.3 to 7.4
-0.7 to 7.4
-40 to +150
-65 to +150
+300
20
100
4000
200
Unit
V
V
V
V
ºC
ºC
ºC
ºC/W
ºC/W
V
V
Notes:
5. Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and
functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Conditions” is not implied.
Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability.
6. The device is mounted on FR-4 substrate PCB, 2 oz copper, with 1 inch2 pad.
Electrical Characteristics (@VCC=15V, TA=+25°C, unless otherwise specified.)
Symbol
Parameter
STARTUP AND UVLO SECTION
VTH_ST
Startup Threshold
VOPR(MIN)
Minimum Operating Voltage
STANDBY CURRENT SECTION
IST Startup Current
ICC_NL
ICC_OPR
Standby Current
Operating Current
DRIVING OUTPUT SECTION
VGATE
Gate Voltage
ISOURCE_PEAK Peak Driver Source Current
RDS(ON)
Sink Resistance
Conditions
–
–
VCC=VTH_ST-1V before
startup
At no load
Static current
–
–
–
Min
11
5.5
0
5
350
9
15
2
Typ
13
5.9
0.2
17.5
450
10.5
20.5
2.3
Max
15
6.3
0.6
30
550
12
26
2.6
Unit
V
V
A
V
mA
AP3785T
Document number: DS37552 Rev. 4 - 2
5 of 18
www.diodes.com
September 2015
© Diodes Incorporated
5 Page 
AP3785T
Operation Principle Description (Cont.)
So the power transferring from the input to the output is given by:
P
1
2
LM
IPK 2
f SW
(9)
1
2
LP
I PK 2
fSW
PO
VO
IO
(10)
Where, fSW is the switching frequency, η is the transferring efficiency.
In AP3785T, the high load mode and light load mode adopt the frequency modulation (FM), and the middle load mode uses the amplitude
modulation (AM).
During FM, the peak current IPK is constant, the output power depends on the switching frequency fSW.
During AM, the frequency is fixed, VCS_M is varied. Below is the analysis of VCS_M。
The square root equation can be got from the following equation:
1
2
L
P
I PK 2
fSW
1
2
L
P
VCS
R CS
2
fSW
VO
IO
So, VCS
2
R
2
CS
VO
IO
Lp fSW
(11)
(12)
During AM, the frequency is fixed, assume VO and η are constants, then
VCS k IO
( k
2
R
2
CS
VO
)
Lp fSW
(13)
7. NL Mode Operation (Typical Application with APR3415)
At no load and ultra light load, the AP3785T works at no load mode (NL mode) and the output voltage is detected by APR3415. In order to
achieve ultra low standby power at NL mode, the static current is reduced to ICC_NL.
• The conditions of exiting NL mode---VCBC> VCBC(EN) or tOFF< tOFF(EX)
• The conditions of entering NL mode-- VCBC< VCBC(EN) and tOFF≥tOFF(EN)
At NL mode, the internal reference voltage VDD is pulled to ground. For normal NL working state, when the APR3415 detects the output voltage is
lower than its trigger voltage. The APR3415 VDET pin emits a periodical pulse current. This pulse current will generate a pulse voltage on
feedback winding through the transformer coupling. When the FB pin detects this pulse (>VTRIGGER is valid), the AP3785T re-establishes the VDD
and turns on primary switch to provide one energy pulse to supply output terminal and primary VCC voltage.
8. Leading Edge Blanking
When the power switch is turned on, a turn-on spike will occur on the sense-resistor. To avoid false-termination of the switching pulse, a leading-
edge blanking (from power MOSFET on) is built in. During this blanking period, the current sense comparator is disabled and the gate driver can’t
be switched off.
9. Valley Turn-on
When the off time (tOFF) is lower than tVAL-ON, AP3785T power system can work with valley turn-on. It can reduce MOSFET switching on power
losses which is resulted from the equivalent output capacitance to achieve highest overall efficiency. At the same time, because of valley turn-on
the switching frequency has the random jitter feature, which will be benefit for conductive EMI performance. And valley turn-on can also reduce
the power switch turn on spike current and then achieve the better radiative EMI performance.
AP3785T
Document number: DS37552 Rev. 4 - 2
11 of 18
www.diodes.com
September 2015
© Diodes Incorporated
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AP3785T.PDF ] | |
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