IS31LT3932

IS31LT3932
HIGH PF LOW THD UNIVERSAL LED DRIVER
December 2013
GENERAL DESCRIPTION
FEATURES
IS31LT3932 is a universal LED driver, which can
operate in fly-back, buck-boost and buck convertor.
For isolation fly-back, it can achieve high PF, high
current accuracy, ±5% load and line regulation and
wide voltage input voltage range, without loop
compensation. For buck convertor, it also can
achieve high PF, high current accuracy, high
efficiency, good load and line regulation and wide
voltage input voltage range, without loop
compensation. With few external components.
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IS31LT3932 has special power line sense and
output voltage sense circuits, operates in primary
feedback mode without Opto-coupler and achieve
stable output current control without any loop
compensation.
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IS31LT3932 has multiple protections to improve the
system reliability, including LED open circuit, LED
short circuit, UVLO, OVP, current sense resistor
short, the primary over current limit and over
temperature protections.
Universal isolation and non-isolation
Single stage PFC fly-back
No loop compensation required
No Opto-coupler required
± 3%LED current accuracy
± 5% line regulation and load regulation
Wide input voltage: 85Vac~265Vac
Low start-up current (15µA)
Valley turn-on MOSFET to achieve high
efficiency for buck application
Few external components
UVLO,OCP,OVP and OTP protections
SOP-8 package
APPLICATION
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LED bulb
LED tube lamp
LED PAR
TYPICAL OPERATING CIRCUIT
Figure 1 Typical isolated Operating Circuit
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
1
IS31LT3932
PIN CONFIGURATIONS
Package
Top View
SOP-8
PIN DESCRIPTIONS
Pin
Name
Function
1
VSINE
Power line voltage detection.
2
OPT
Isolation and non-isolation option PIN.
-Floating: fly-back and buck-boost
-Connect to ground: buck sinusoidal.
Time setting through the resistor between PIN and ground.
-Isolation: operation cycle time setting
3
CT
f  50k 
VFB
300

0.8V Rct (k)
-Non-isolation: MOSFET turn-off delay time setting when FB
detects zero voltage
Tdelay  15  106  REXT
4
GND
Ground.
5
FB
Fly-back and buck-boost: operation frequency is regulated
through this PIN to compensate output current
Non-isolation: valley turn-on detect PIN, the external MOS turns
on after a short delay when FB detects zero voltage
6
CS
MOSFET switching Current sense Pin.
7
GATE
Driver output to the external Power MOSFET.
8
VCC
Power supply input PIN, at a range of 8V~30V.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
2
IS31LT3932
ORDERING INFORMATION
Industrial Range: -40°C to +85°C
Order Part No.
Package
QTY/Reel
IS31LT3932-GRLS2-TR
SOP-8, Lead-free
2500
Copyright © 2013 Integrated Silicon Solution, Inc. All rights reserved. ISSI reserves the right to make changes to this specification and its products at any time without notice. ISSI assumes no liability arising out of the application or use of any information, products or services described herein. Customers are advised to obtain the latest version of this device specification before relying on any published information and before placing orders for products. Integrated Silicon Solution, Inc. does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless Integrated Silicon Solution, Inc. receives written assurance to its satisfaction, that: a.) the risk of injury or damage has been minimized; b.) the user assume all such risks; and c.) potential liability of Integrated Silicon Solution, Inc is adequately protected under the circumstances
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
3
IS31LT3932
ABSOLUTE MAXIMUM RATINGS
VCC,GATE to GND
VSINE, OPT, CT, ISEN, FB to GND
Operating temperature, TA
Storage temperature, TST
Junction temperature, TJMAX
ESD (HBM)
ESD (CDM)
-0.3V ~ 36V
-0.3V ~ 6.0V
-40°C ~ +85°C
-60°C ~ +150°C
150°C
2.5kV
750V
Note:
Stresses beyond 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 condition beyond those indicated in the operational sections of the specifications is
not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
Unless otherwise specified, VCC=16V, VFB=0V, VSINE=0V, VCS=0V, OPT Floating, RSET=300k, and TA=25°C.
Symbol
Parameter
Condition
Min
Type
Unit
30
V
VCC
Power supply range
VOVP
VCC over voltage threshold
33.5
V
tOVP
OVP reset time
160
ms
VST
Startup voltage
VCC rising
14.5
16.0
17.5
V
Under voltage lockout
VCC falling
6
7
8
V
GATE output clamp voltage
VCC=22V
14
16.5
19
V
IIN
Quiescent current
without switching
750
1000
µA
IST
Startup current
VCC=<Vth_s
15
20
µA
500
507
mV
550
800
ns
1.2
1.24
1.28
V
140
160
180
ms
VUVLO
VGATE_CLP
8
Max
VCSTH
Peak current voltage threshold
tBLANK
Current sense blanking time
VFB,OVP
FB pin over voltage threshold
tFB,OVP
FB OVP reset time
VOCP
Over current voltage threshold
650
700
750
mV
TOCP
OCP reset time
35
40
45
ms
tOFF_MIN
tCYCLE
Minimum TOFF time
Operating cycle
493
VCS=VCSTH+50mV
tCYCLE = 20µs
OPT=0
1
µs
VFB=0.8V, RCT=300kΩ
19.6
20
20.4
µs
VFB=1.04V, RCT=300kΩ
15.2
15.6
16.0
µs
VFB=0.56V, RCT=300kΩ
27.7
28.3
28.9
µs
VOCP
Over current voltage threshold
700
mV
tOCP
OCP reset time
40
ms
tR
Rise time
VCC=16V,CL=1nF,
VGATE from 0 to 7V
75
90
ns
tF
Fall time
VCC=16V,CL=1nF
40
50
ns
TSD
Thermal shutdown threshold
150
°C
THYS
Thermal shutdown hysteresis
20
°C
tRE
CS short protection reset time
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
35
40
45
ms
4
IS31LT3932
TYPICAL PERFORMANCE CHARACTERISTICS
1.00
20
10LED 9LED
0.98
IOUT = 190mA
8LED
0.96
15
7LED
0.94
THD+N (%)
6LED
PF
0.92
5LED
0.90
0.88
10
VIN = 220VAC
0.86
5
VIN = 110VAC
0.84
0.82
0.80
85
IOUT = 190mA
105
125
145
165
185
205
225
245
0
15
265
18
PF vs. Power Supply
Figure 3
200
Output Current (mA)
Output Current (mA)
120
100
80
180
THD+N vs. Output Voltage
150
140
130
40
120
20
110
125
145
165
185
205
225
245
VIN = 110VAC
160
60
105
VIN = 220VAC
170
IOUT = 190mA
100
15
265
18
Figure 4
21
24
27
30
Output Voltage (V)
Power Supply (VAC)
Output Current vs. Power Supply
Figure 5
Output Current vs. Output Voltage
100
100
IOUT = 190mA
IOUT = 190mA
95
95
90
90
85
6LED
7LED
80
Efficiency (%)
Efficiency (%)
30
190
IOUT = 190mA
5LED ~ 10LED
140
0
85
27
200
180
160
24
Output Voltage (V)
Power Supply (VAC)
Figure 2
21
10LED 9LED
85
80
8LED
5LED
75
75
70
85
105
125
145
165
185
205
225
245
265
70
85
105
125
Efficiency vs. Power Supply
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
165
185
205
225
245
Power Supply (VAC)
Power Supply (VAC)
Figure 6
145
Figure 7
Efficiency vs. Power Supply
5
265
IS31LT3932
FUNCTIONAL BLOCK DIAGRAM
Vsupply
vdda
Rin
Voltage Regulator
16.5V
VCC
ovp
33V OVP
10uF
0.7V
CMP1
ocp
CS
VSINE
CMP1
AGC
R
NMOS
S
FB
ZCS
GATE driver logic
Valley Detec
Driver
GATE
CT
OSC
Rcs
OPT
Por
Function
Switch
UVLO
CMP1
fb_ovp
1.24V
GND
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
6
IS31LT3932
APPLICATION INFORMATION
Base on Figure 17 & Figure 18 Typical Application Circuit
FUNCTION DESCRIPTION
For fly-back or buck-boost when OPT is floating, the
operation cycle will be set by the external resistor of
CT-PIN through the output clock of OSC block , the
GATE will be turned on at the rising edge of clock
and turn off when CS voltage hit AGC output. Also,
other signal, such as OCP and OVP, can turn off
GATE directly.
VCC
Ip-pk
AGC output is a synchronized half-sinusoid
waveform with constant peak, as the input halfsinusoid with variable peak.
For buck when OPT connects to ground, the only
difference is that GATE turn on is determined by the
Zero-Cross-Switch block with a short delay of Valley
Detect, but not the former rising-edge of clock.
STARTUP VOLTAGE
When the rectified AC voltage is applied to the R6,
R10 & C9 a startup circuit, this C9 will be started to
be charged. The IC will start working when the
voltage of C9 reaches 16V of the start threshold for
the IC. The value of R6 and R10 & C9 can be
determined by the input voltage & start threshold
voltage. The bigger values of R6 and R10 used will
increase the startup time, but can reduce the loss of
power consumption at the whole operation time. R6
& R10 =300kΩ, 1206 size is recommend. A low ESR
capacitor of 4.7~10µF, 50V is recommended for C9.
VCC
Figure 9
Soft Start
GATE OUTPUT VOLTAGE CLAMP
IS31LT3932 has the voltage clamp function for
GATE output. When the voltage of VCC is smaller
than the VGATE_clp threshold, the voltage of GATE
output is about VCC. When VCC voltage is greater
than VGATE_clp threshold, the GATE voltage is
clamped same with VGATE_clp threshold voltage.
VCC
GATE
Figure 10
Gate Voltage Clamped
VSINE DETECTION NETWORK AND ACTIVE PFC
GATE
Figure 8
Start-up
SOFT START CONTROL
When Vcc is reached the start the threshold voltage,
the CS voltage is forced increasing from low limit
level go to 0.5V cycle by cycle. So the switching
current will be slow increased to achieve the soft
start.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
The Pin VSINE is used to detect the input voltage
which controls the peak current waveform in the
inductor to follow Line AC voltage and let inside
AGC makes the peak current of inductor constant,
so that allows the IS31LT3932 to actively correct the
power factor and constant power during operation.
The maximum input voltage of the VSINE pin is 2.5V.
This resistor network should be computed such that
the peak input voltage condition corresponds to
0.75~2.5VDC. When input AC is 265VAC, the peak
voltage is 374.7V and the output of the network
should be 2.4V, thus values of R5+R9=2MΩ, its size
is 1206 and R18 = 13kΩ are appropriate and
recommend to use 1% of tolerance resister. A
small1nF capacitor, C7, is used to filter high
frequency noise.
7
IS31LT3932
VCC
Vbulk
Ip-pk
GATE
Figure 11
Active PFC
OPERATING FREQUENCY
The working frequency is set by connecting a
resistor between the CT pin and ground. The
relationship between the frequency and resistance is:
f  50k 
VFB
300

0.8V RCT (k)
OUTPUT OPEN CIRCUIT PROTECTION
Open circuit protection is realized by connecting a
resistor network to the FB pin. By sensing the
voltage of the auxiliary winding, which is proportional
to the output voltage, the IS31LT3932 detects when
there is an open circuit condition on the secondary
and stop the switching action. The threshold voltage
for the FB pin is 1.24V. When it is great than 1.24V,
the GATE will output the 160ms low level signal to
tuned off the MOSFET until the fail is removed.
Figure 13
Output Short Circuit Protect
The device will not operate if the VCC voltage is
below the under-voltage lockout threshold cycle by
cycle, until the VCC voltage is higher than the
threshold, and then the device will start working
again.
CS OVER CURRENT AND SHORT PROTECTION
If the output LEDs is shorted or some components
were failed, Vcs voltage will rise very quickly. If this
Vcs voltage is over than 0.7V threshold voltage, the
MOSFET gate will be turned off 40ms and then
continue keep detecting Vcs voltage cycle by cycle
until the fault condition removed.
If the CS pin is shorted, others IC no longer detect
the peak switching current, but 3932 IC integrates a
maximum duty cycle protection circuit when if a duty
cycle occupied up to 100% within one logic stage,
the Gate pin will output a low level 40ms to turn off
MOSFET until the fault removed.
Please see Figure 13 Output Short Circuit Protection.
LINE & LOAD REGULATION
VCC
GATE
Figure 12
OVP
UVLO PROTECTION
If the output of the circuit is suddenly shorted, then
the voltage of the secondary winding is quickly
reduced, and also it will be reflected into the auxiliary
winding, so VCC of the device will drop rapidly. If the
VCC voltage drops below the UVLO’ threshold, the
device will stop switching, thus indirectly achieving
output short circuit protection and UVLO protection.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
In order to ensure that at different AC line voltage,
the output current is constant, an AGC (Automatic
Gain Control) is used, its output signal is as CS
threshold voltage and set threshold peak voltage is
0.5V as typical value. The transformer peak current
IL is controlled by CS threshold, if the peak current
of transformer is constant by mean of changing
operation frequency to maintain a constant current &
AGC in DCM model, then the input power is
constant in all input voltage range and output current
is constant in all input voltage range.
As the number of LED lights load changed, the
output voltage will change, that caused the
transformer auxiliary winding voltage will follow this
changes.
This voltage can be determined the number of LED
and is feed into the FB pin for proportional adjusting
the operation frequency of IC to achieve constant
output current when loading changed. Please refer
to the specific operating frequency calculation
description.
8
IS31LT3932
The FB pin voltage is in the range of 0.5~1.25V, the
control voltage is proportional to the frequency and
FB, when the FB voltage is less than 0.5V, the
frequency remained unchanged.
When 3932 works under BUCK application, Pin 2
will be connected to ground. The inductor current
works on the CRM model, the Iout current is 0.5IL in
the single working cycle. The solid line is the
inductor current waveform when the MOS transistor
is turned on, the dotted line is the inductor current for
the MOS transistor is turned off. The AGC function
can maintain a constant IL and work at CRM mode,
then the output current Iout will be constant.
PCB DESIGN CONSIDERATIONS
(1) As Figure15 and 16 shows, components such as
C7, R17, R18, R20, R21, R22, R23, C9 etc.
which are connected to the IC should be
mounted as close to the IC as possible.
(2) Bypass capacitors should always be mounted as
close to the IC as possible.
(3) Switching signal traces should be kept as short
as possible and not be routed parallel to one
another so as to prevent coupling.
To detect the auxiliary winding voltage when the
zero current happened and turn on MOSFET as
soon, the zero current switching can be achieved;
also the CRM model can be achieved. System works
in FM mode (Figure 14).
Figure 15 Typical PCB Top Layer
Figure 16 Typical PCB Bottom Layer
Figure 14
Inductor Switching Current
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Rev. A, 11/28/2013
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IS31LT3932
TYPICAL APPLICATION CIRCUIT
It is suited to full input voltage 15~30V-0.2A output applications
Figure 17 Typical Isolated Application Schematic
Figure 18 Typical Non-Isolated Application Schematic
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Rev. A, 11/28/2013
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IS31LT3932
CLASSIFICATION REFLOW PROFILES
Profile Feature
Pb-Free Assembly
Preheat & Soak
Temperature min (Tsmin)
Temperature max (Tsmax)
Time (Tsmin to Tsmax) (ts)
150°C
200°C
60-120 seconds
Average ramp-up rate (Tsmax to Tp)
3°C/second max.
Liquidous temperature (TL)
Time at liquidous (tL)
217°C
60-150 seconds
Peak package body temperature (Tp)*
Max 260°C
Time (tp)** within 5°C of the specified
classification temperature (Tc)
Max 30 seconds
Average ramp-down rate (Tp to Tsmax)
6°C/second max.
Time 25°C to peak temperature
8 minutes max.
Figure 19 Classification Profile
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Rev. A, 11/28/2013
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IS31LT3932
PACKAGE INFORMATION
SOP-8
Note: All dimensions in millimeters unless otherwise stated.
Integrated Silicon Solution, Inc. – www.issi.com
Rev. A, 11/28/2013
12