LT3796 Datasheet PDF - Linear Technology

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LT3796
Linear Technology

Part Number LT3796
Description 100V Constant-Current and Constant-Voltage Controller
Page 30 Pages


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FEATURES
n 3000:1 True Color PWM™ Dimming
n Wide Input Voltage Range: 6V to 100V
n Current Monitoring Up to 100V
n High Side PMOS Disconnect and PWM Switch Driver
n Constant-Current and Constant-Voltage Regulation
n Dual Current Sense Amplifiers with Reporting
n C/10 Detection for Battery and SuperCap Charging
n Linear Current Sense Threshold Programming
n Short-Circuit Protection
n Adjustable Frequency: 100kHz to 1MHz
n Frequency Synchronization
n Programmable Open LED Protection with VMODE Flag
n Programmable Undervoltage Lockout with Hysteresis
n Soft-Start with Programmable Fault Restart Timer
n Low Shutdown Current: <1μA
n Available in 28-Lead TSSOP Package
APPLICATIONS
n High Power LED, High Voltage LED
n Battery and SuperCap Chargers
n Accurate Current Limited Voltage Regulators
LT3796
100V Constant-Current and
Constant-Voltage Controller
with Dual Current Sense
DESCRIPTION
The LT®3796 is a DC/DC controller designed to regulate a
constant-current or constant-voltage and is ideal for driv-
ing LEDs. It drives a low side external N-channel power
MOSFET from an internal regulated 7.7V supply. The fixed
frequency and current mode architecture result in stable
operation over a wide range of supply and output volt-
ages. Two ground referred voltage FB pins serve as the
input for several LED protection features, and also allow
the converter to operate as a constant-voltage source.
The LT3796 features a programmable threshold output
sense amplifier with rail-to-rail common mode range. The
LT3796 also includes a separate high side current sensing
amplifier that is gain configurable with two resistors. The
TG pin inverts and level shifts the PWM signal to drive
the gate of the external PMOS. The PWM input provides
LED dimming ratios of up to 3000:1, and the CTRL input
provides additional analog dimming capability.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and True
Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 7199560, 7321203,
7746300.
TYPICAL APPLICATION
VIN
9V TO 60V
100V (TRANSIENT)
CSOUT
INTVCC
FAULT
VMODE
Boost LED Driver with Input Current Monitor
50mΩ
22µH
2.2µF
×3
1M
118k
10nF 40.2k
100k 100k
2k
499k
97.6k
PWM
0.1µF
VIN
EN/UVLO
VREF
CTRL
CSOUT
PWM
ISMON
SYNC
VS CSP
LT3796
CSN
GATE
SENSE
GND
FB1
ISP
ISN
FAULT
VMODE
VC RT
FB2
10nF
10k
31.6k
250kHz
TG
INTVCC
SS
0.1µF
15mΩ
INTVCC
4.7µF
1M
13.7k
2.2µF
×4
620mΩ
85V LED
400mA
3796 TA01a
Efficiency vs VIN
100
95
90
85
80
75
70
0 10 20 30 40 50 60
VIN (V)
3796 TA01b
3796f
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LT3796
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN, VS.....................................................................100V
EN/UVLO.................................................................. 100V
ISP, ISN....................................................................100V
TG, GATE...............................................................Note 3
CSP, CSN.................................................................100V
VS - CSP, VS - CSN........................................ –0.3V to 4V
INTVCC (Note 2)......................................8.6V, VIN + 0.3V
PWM, VMODE, FAULT................................................12V
FB1, FB2, SYNC............................................................8V
CTRL.......................................................................... 15V
SENSE.......................................................................0.5V
ISMON, CSOUT............................................................5V
VC, VREF, SS.................................................................3V
RT................................................................................2V
Operating Junction Temperature Range (Note 4)
LT3796E/LT3796I................................... –40 to 125°C
LT3796H................................................. –40 to 150°C
Storage Temperature Range.......................–65 to 150°C
PIN CONFIGURATION
TOP VIEW
ISP 1
28 CSOUT
ISN 2
27 CSP
TG 3
26 CSN
GND 4
25 VS
ISMON 5
24 EN/UVLO
FB2 6
23 VIN
FB1 7 29 22 GND
VC 8 GND 21 GND
CTRL 9
20 INTVCC
VREF 10
SS 11
19 GATE
18 SENSE
RT 12
17 GND
SYNC 13
16 VMODE
PWM 14
15 FAULT
FE PACKAGE
TJMA2X8=-L15E0A°DC,PθLJAA S=T3I0C°CT/SWS, OθJPC = 10°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LT3796EFE#PBF
LT3796EFE#TRPBF
LT3796FE
28-Lead Plastic TSSOP
–40°C to 125°C
LT3796IFE#PBF
LT3796IFE#TRPBF
LT3796FE
28-Lead Plastic TSSOP
–40°C to 125°C
LT3796HFE#PBF
LT3796HFE#TRPBF
LT3796FE
28-Lead Plastic TSSOP
–40°C to 150°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
3796f
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LT3796
E LECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 24V, EN/UVLO = 24V, CTRL = 2V, PWM = 5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
VIN Minimum Operating Voltage
VIN Shutdown IQ
VIN Tied to INTVCC
EN/UVLO = 0V, PWM = 0V
EN/UVLO = 1.15V, PWM = 0V
6V
1 µA
12 µA
VIN Operating IQ (Not Switching)
VREF Voltage
VREF Pin Line Regulation
VREF Pin Load Regulation
SENSE Current Limit Threshold
RT = 82.5k to GND, FB1 = 1.5V
–100µA ≤ IREF ≤ 10µA
6V < VIN < 100V
–100µA < IREF < 0µA
l 1.97
l 100
2.5
2.015
1.5
10
113
3 mA
2.06 V
m%/V
m%/µA
125 mV
SENSE Input Bias Current
Current Out of Pin
60 µA
SS Sourcing Current
SS = 0V
28 µA
SS Sinking Current
ISP – ISN = 1V, SS = 2V
2.8 µA
Error Amplifier
Full Scale LED Current Sense Threshold
(V(ISP-ISN))
9/10th LED Current Sense Threshold
(V(ISP-ISN))
1/2 LED Current Sense Threshold
(V(ISP-ISN))
1/10th LED Current Sense Threshold
(V(ISP-ISN))
ISP/ISN Current Monitor Voltage (VISMON)
ISP/ISN Over Current Protection Threshold
(V(ISP-ISN))
CTRL Input Bias Current
ISP = 48V, CTRL ≥ 1.2V
ISP = 0V, CTRL ≥ 1.2V
CTRL = 1V, ISP = 48V
CTRL = 1V, ISP = 0V
CTRL = 0.6V, ISP = 48V
CTRL = 0.6V, ISP = 0V
CTRL = 0.2V, ISP = 48V
CTRL = 0.2V, ISP = 0V
VV((IISSPP--IISSNN))
=
=
250mV,
250mV,
ISP = 48V, –50µA
ISP = 0V, –50µA
<
<
IIIISSMMOONN
<
<
0
0
µA
µA
ISN = 48V
ISN = 0V
Current Out of Pin, CTRL = 1.2V
l
l
l
l
l
l
l
l
l
l
l
l
243
243
220
220
119
119
16
16
0.96
0.96
360
360
250 257
250 257
225 230
225 230
125 131
125 131
25 32
25 32
1 1.04
1 1.04
375 390
375 390
50 200
mV
mV
mV
mV
mV
mV
mV
mV
V
V
mV
mV
nA
ISP/ISN Current Sense Amplifier Input
Common Mode Range
0 100 V
ISP/ISN Input Current Bias Current
(Combined)
PWM = 5V (Active), ISP = 48V
PWM = 0V (Standby), ISP = 48V
700
0 0.1
µA
µA
ISP/ISN Current Sense Amplifier gm
VC Output Impedance
VC Standby Input Bias Current
FB1, FB2 Regulation Voltage (VFB)
V(ISP-ISN) = 250mV
PWM = 0V
ISP = ISN = 48V
ISP = ISN = 48V
–20
l 1.230
1.238
400
2000
1.250
1.250
20
1.270
1.264
µs
nA
V
V
FB1 Amplifier gm
FB2 Amplifier gm
FB1, FB2 Pin Input Bias Current
FB1 Open LED Threshold
C/10 Comparator Threshold (V(ISP-ISN))
FB = VFB
VMODE Falling, ISP = ISN = 48V
VMODE Falling, FB1 = 1.5V, ISP = 48V
VMODE Falling, FB1 = 1.5V, ISN = 0V
800 1000 1200
130 170 210
100 200
VFB – 70mV VFB – 60mV VFB – 50mV
25
25
µS
µS
nA
V
mV
mV
FB1 Overvoltage Threshold
FB2 Overvoltage Threshold
VC Current Mode Gain (∆VVC/∆VSENSE)
FAULT Falling
TG Rising
VFB + 35mV
VFB + 35mV
VFB + 50mV VFB + 60mV
VFB + 50mV VFB + 60mV
4.2
V
V
V/V
3796f
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LT3796
E LECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C, VIN = 24V, EN/UVLO = 24V, CTRL = 2V, PWM = 5V, unless otherwise noted.
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
Current Sense Amplifier (CSA)
Power Supply Voltage Range (VS)
CSA Input Voltage Common Mode Range
(VCSP and VCSN)
CSOUT Maximum Output Current
CSOUT = 10kΩ to GND
l3
l 2.5
l
100 V
100 V
200 µA
Input Voltage Offset (V(CSP-CSN))
VSNS = 100mV, VS = 48V (Note 5)
l –3 0 3 mV
CSP, CSN Input Bias Current
VSNS = 0mV, RIN1 = RIN2 = 1k (Note 5)
100 nA
CSP, CSN Input Current Offset
VSNS = 0mV, RIN1 = RIN2 = 1k (Note 5)
0 nA
VS Supply Current
VS = 48V
80 µA
Input Step Response ( to 50% of Output Step) ∆VSENSE = 100mV Step, RIN1 = RIN2 = 1k, ROUT = 10k
1 µs
Linear Regulator
INTVCC Regulation Voltage
Dropout (VIN– INTVCC)
INTVCC Current Limit
DINrTivVeCnCtSoh7uVtdown Bias Current if Externally
IINTVCC = –20mA, VIN = 6V
VVIINN
=
=
11020V,VI,NINTVTVCCCC==6V6V
EN/UVLO = 0V, INTVCC = 7V
l 7.4 7.7 8
V
400 mV
20 mA
85 mA
10 µA
INTVCC Undervoltage Lockout
INTVCC Undervoltage Lockout Hysteresis
Oscillator
3.8 4 4.1 V
150 mV
Switching Frequency
Minimum Off-Time
RT = 82.5k
RT = 19.6k
RT = 6.65k
(Note 6)
l 85
l 340
l 900
105 125
400 480
1000 1150
190
kHz
kHz
kHz
ns
Minimum On-Time
(Note 6)
210 ns
LOGIC Input/Outputs
PWM Input Threshold Rising
l 0.96
1 1.04
V
PWM Pin Bias Current
10 µA
EN/UVLO Threshold Voltage Falling
l 1.185
1.220
1.250
V
EN/UVLO Rising Hysteresis
20 mV
EN/UVLO Input Low Voltage
EN/UVLO Pin Bias Current Low
IVIN Drops Below 1µA
EN/UVLO = 1.15V
0.4 V
2.5 3 3.8 µA
EN/UVLO Pin Bias Current High
EN/UVLO = 1.30V
40 200 nA
VMODE OUTPUT Low
FAULT OUTPUT Low
SYNC Pin Resistance to GND
IVMODE = 0.5mA
IFAULT = 0.5mA
300 mV
300 mV
40 kΩ
SYNC Input Low Threshold
0.4 V
SYNC Input High Threshold
1.5 V
3796f
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