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LTC3836EGN#PBF

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LTC3836
1
3836fb
FEATURES
APPLICATIONS
DESCRIPTION
Dual 2-Phase,
No R
SENSE
TM
Low V
IN
Synchronous Controller
The LTC
®
3836 is a 2-phase dual output synchronous
step-down switching regulator controller with tracking
that drives external N-channel power MOSFETs using few
external components. The constant-frequency current
mode architecture with MOSFET V
DS
sensing eliminates
the need for sense resistors and improves effi ciency.
The power loss and noise due to the ESR of the input
capacitance are minimized by operating the two control-
lers out-of-phase. Pulse-skipping operation provides high
effi ciency at light loads. The 97% duty cycle capability
provides low dropout operation, extending operating time
in battery-powered systems.
The operating frequency is selectable from 300kHz to
750kHz, allowing the use of small surface mount induc-
tors and capacitors. For noise sensitive applications, the
LTC3836 operating frequency can be externally synchro-
nized from 250kHz to 850kHz.
The LTC3836 features an internal 1ms soft-start that can
be extended with an external capacitor. A tracking input al-
lows the second output to track the fi rst during start-up.
The LTC3836 is available in the tiny thermally enhanced
(4mm × 5mm) QFN and 28-lead narrow SSOP packages.
High Effi ciency, 2-Phase, Dual Synchronous DC/DC Step-Down Converter
n
No Current Sense Resistors Required
n
Out-of-Phase Controllers Reduce Required Input
Capacitance
n
All N-Channel Synchronous Drive
n
V
IN
Range: 2.75V to 4.5V
n
Constant-Frequency Current Mode Operation
n
0.6V ±1.5% Voltage Reference
n
Low Dropout Operation: 97% Duty Cycle
n
True PLL for Frequency Locking or Adjustment
n
Selectable Pulse-Skipping/Continuous Operation
n
Tracking Function
n
Internal Soft-Start Circuitry
n
Power Good Output Voltage Monitor
n
Output Overvoltage Protection
n
Micropower Shutdown: I
Q
= 6.5μA
n
Tiny Low Profi le (4mm × 5mm) QFN and Narrow
SSOP Packages
n
General Purpose 3.3V to 1.X Supplies
n
Single Lithium-Ion Powered Devices
n
Distributed DC Power Systems
SENSE1
+
V
IN
LTC3836
SGND
SENSE2
+
BOOST1 BOOST2
TG1 TG2
SW1 SW2
BG1 BG2
PGND
V
FB1
V
FB2
820pF
V
OUT1
1.8V AT
15A
V
OUT2
1.2V AT
15A
100μF
× 2
100μF
× 2
15k
820pF
15k
59k
59k
118k
59k
0.47μH
0.47μH
I
TH1
3836 TA01
I
TH2
22μF
× 3
V
IN
3.3V
Effi ciency/Power Loss vs Load Current
LOAD CURRENT (mA)
30
EFFICIENCY (%)
POWER LOSS (mW)
90
100
20
10
80
50
70
60
40
100 1000 10000010000
3836 TA01b
0
10000
10
100
1000
1
10
3.3V-1.2V
POWER LOSS
CIRCUIT OF FIGURE 15
3.3V-1.2V
EFFICIENCY
3.3V-1.8V
EFFICIENCY
3.3V-1.8V
POWER LOSS
TYPICAL APPLICATION
L, LT, LTC, LTM, Linear Technology, Burst Mode, OPTI-LOOP and the Linear logo are
registered trademarks and No R
SENSE
is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners. Protected by U.S. Patents including
5481178, 5929620, 6144194, 6304066, 6498466, 6580258, 6611131.
LTC3836
2
3836fb
ABSOLUTE MAXIMUM RATINGS
BOOST1, BOOST2 Voltages ....................... –0.3V to 10V
Input Supply Voltage (V
IN
) ........................ –0.3V to 4.5V
PLLLPF, RUN/SS, SYNC/FCB,
SENSE1
+
, SENSE2
+
,
IPRG1, IPRG2 Voltages ..................–0.3V to (V
IN
+ 0.3V)
V
FB1
, V
FB2
, I
TH1
, I
TH2
,
TRACK/SS2 Voltages ................................ –0.3V to 2.4V
(Note 1)
PARAMETER CONDITIONS MIN TYP MAX UNITS
Main Control Loops
Input DC Supply Current
Normal Mode
Shutdown
UVLO
(Note 4)
RUN/SS = V
IN
RUN/SS = 0V
V
IN
= UVLO Threshold –200mV
450
6.5
4
700
15
10
μA
μA
μA
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 3.3V unless otherwise specifi ed.
SW1, SW2 Voltages ............................... –2V to V
IN
+ 1V
PGOOD ....................................................... –0.3V to 10V
Operating Temperature Range (Note 2).... –40°C to 85°C
Storage Temperature Range ................... –65°C to 125°C
Junction Temperature (Note 3) ............................. 125°C
1
2
3
4
5
6
7
8
9
10
11
12
13
14
TOP VIEW
GN PACKAGE
28-LEAD PLASTIC SSOP
28
27
26
25
24
23
22
21
20
19
18
17
16
15
SW1
N/C
IPRG1
V
FB1
I
TH1
IPRG2
PLLLPF
SGND
V
IN
TRACK/SS2
V
FB2
I
TH2
PGOOD
SW2
SENSE1
+
BOOST1
PGND
BG1
SYNC/FCB
TG1
PGND
TG2
RUN/SS
BG2
N/C
PGND
BOOST2
SENSE2
+
T
JMAX
= 125°C, θ
JA
= 90°C/W
9 10
TOP VIEW
UFD PACKAGE
28-LEAD (4mm × 5mm) PLASTIC QFN
11 12 13
28 27 26
29
25 24
14
23
6
5
4
3
2
1
VFB1
ITH1
IPRG2
PLLLPF
SGND
V
IN
TRACK/SS2
VFB2
BG1
SYNC/FCB
TG1
PGND
TG2
RUN/SS
N/C
BG2
N/C
IPRG1
SW1
SENSE1
+
BOOST1
PGND
ITH2
PGOOD
SW2
SENSE2
+
BOOST2
PGND
7
17
18
19
20
21
22
16
8
15
T
JMAX
= 125°C, θ
JA
= 43°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
PIN CONFIGURATION
ORDER INFORMATION
LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE
LTC3836EGN#PBF LTC3836EGN#TRPBF LTC3836EGN 28-Lead Plastic SSOP –40°C to 85°C
LTC3836EUFD#PBF LTC3836EUFD#TRPBF 3836 28-Lead (4mm × 5mm) Plastic QFN –40°C to 85°C
Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based fi nish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/
ELECTRICAL CHARACTERISTICS
LTC3836
3
3836fb
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC3836 is guaranteed to meet specifi ed performance from
0°C to 85°C. Specifi cations over the –40°C to 85°C operating range are
assured by design, characterization and correlation with statistical process
controls.
PARAMETER CONDITIONS MIN TYP MAX UNITS
Undervoltage Lockout Threshold V
IN
Falling
V
IN
Rising
l
l
1.95
2.15
2.25
2.45
2.55
2.75
V
V
Shutdown Threshold at RUN/SS 0.45 0.65 0.85 V
Start-Up Current Source RUN/SS = 0V 0.4 0.65 1 μA
Regulated Feedback Voltage –40°C to 85°C (Note 5)
l
0.591 0.6 0.609 V
Output Voltage Line Regulation 2.75V < V
IN
< 4.5V (Note 5) 0.05 0.2 mV/V
Output Voltage Load Regulation I
TH
= 0.9V (Note 5)
I
TH
= 1.7V
0.12
–0.12
0.5
–0.5
%
%
V
FB1,2
Input Current (Note 5) 10 50 nA
TRACK/SS2 Input Current TRACK/SS2 = 0V 1 1.5 2.2 μA
Overvoltage Protect Threshold Measured at V
FB
0.66 0.68 0.7 V
Overvoltage Protect Hysteresis 20 mV
Auxiliary Feedback Threshold SYNC/FCB Ramping Positive 0.525 0.6 0.675 V
Top Gate (TG) Drive 1, 2 Rise Time C
L
= 3000pF 40 ns
Top Gate (TG) Drive 1, 2 Fall Time C
L
= 3000pF 40 ns
Bottom Gate (BG) Drive 1, 2 Rise Time C
L
= 3000pF 50 ns
Bottom Gate (BG) Drive 1, 2 Fall Time C
L
= 3000pF 40 ns
Maximum Current Sense Voltage (∆V
SENSE(MAX)
)
(SENSE
+
– SW)
IPRG = Floating
IPRG = 0V
IPRG = V
IN
l
l
l
110
70
185
122
82
202
135
95
220
mV
mV
mV
Maximum Duty Cycle In Dropout 97 %
Soft-Start Time Time for V
FB1
to Ramp from 0.05V to 0.55V 0.6 0.8 1 ms
Oscillator and Phase-Locked Loop
Oscillator Frequency Unsynchronized (SYNC/FCB Not Clocked)
PLLLPF = Floating
PLLLPF = 0V
PLLLPF = V
IN
480
260
650
550
300
750
600
340
825
kHz
kHz
kHz
Phase-Locked Loop Lock Range SYNC/FCB Clocked
Minimum Synchronizable Frequency
Maximum Synchronizable Frequency
l
l
850
200
1150
250 kHz
kHz
Phase Detector Output Current
Sinking
Sourcing
f
OSC
> f
SYNC/FCB
f
OSC
> f
SYNC/FCB
–4
4
μA
μA
PGOOD Output
PGOOD Voltage Low I
PGOOD
Sinking 1mA 140 mV
PGOOD Trip Level V
FB
with Respect to Set Output Voltage
V
FB
< 0.6V, Ramping Positive
V
FB
< 0.6V, Ramping Negative
V
FB
> 0.6V, Ramping Negative
V
FB
> 0.6V, Ramping Positive
–13
–16
7
10
–10.0
–13.3
10.0
13.3
–7
–10
13
16
%
%
%
%
ELECTRICAL CHARACTERISTICS
The l denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are at T
A
= 25°C. V
IN
= 3.3V unless otherwise specifi ed.
Note 3: T
J
is calculated from the ambient temperature T
A
and power dissi-
pation P
D
according to the following formula: T
J
= T
A
+ (P
D
• θ
JA
°C/W)
Note 4: Dynamic supply current is higher due to gate charge being
delivered at the switching frequency.
Note 5: The LTC3836 is tested in a feedback loop that servos I
TH
to a
specifi ed voltage and measures the resultant V
FB
voltage.
Note 6: Peak current sense voltage is reduced dependent on duty cycle to
a percentage of value as shown in Figure 1.
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LTC3836EGN#PBF

Mfr. #:
Buy LTC3836EGN#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Low Input Voltage 2-Phase Synch Controller w/ Tracking
Lifecycle:
New from this manufacturer.
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