Document
LTC3826-1
30µA IQ, Dual, 2-Phase Synchronous Step-Down Controller
FEATURES
DESCRIPTION
n Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 10V n Low Operating IQ: 30μA (One Channel On) n Out-of-Phase Controllers Reduce Required Input
Capacitance and Power Supply Induced Noise n OPTI-LOOP® Compensation Minimizes COUT n ±1% Output Voltage Accuracy n Wide VIN Range: 4V to 36V Operation n Phase-Lockable Fixed Frequency 140kHz to 650kHz n Selectable Continuous, Pulse Skipping or Low Ripple
Burst Mode® Operation at Light Loads n Dual N-Channel MOSFET Synchronous Drive n Very Low Dropout Operation: 99% Duty Cycle n Adjustable Output Voltage Soft-Start or Tracking n Output Current Foldback Limiting n Power Good Output Voltage Monitor n Output Overvoltage Protection n Low Shutdown IQ: 4μA n Internal LDO Powers Gate Drive from VIN or VOUT n Small 28-Lead SSOP Package
APPLICATIONS
n Automotive Systems n Battery-Operated Digital Devices n Distributed DC Power Systems
The LTC®3826-1 is a high performance dual step-down switching regulator controller that drives all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows a phase-lockable frequency of up to 650kHz. Power loss and noise due to the ESR of the input capacitor ESR are minimized by operating the two controller output stages out of phase.
The 30μA no-load quiescent current extends operating life in battery powered systems. OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3826-1 features a precision 0.8V reference and a power good output indicator. A wide 4V to 36V input supply range encompasses all battery chemistries.
Independent TRACK/SS pins for each controller ramp the output voltage during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions.
The PLLIN/MODE pin selects among Burst Mode operation, pulse skipping mode, or continuous inductor current mode at light loads. For a leadless package version (5mm × 5mm QFN) with additional features, see the LTC3826 data sheet.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 5481178, 5929620, 6177787, 6144194, 5408150, 6580258, 6304066, 5705919.
TYPICAL APPLICATION
VOUT1 3.3V
5A
3.3μH
0.015Ω 62.5k
150μF
High Efficiency Dual 8.5V/3.3V Step-Down Converter
0.1μF
VIN TG1
INTVCC TG2
BOOST1
BOOST2
SW1
SW2
BG1
BG2
LTC3826-1
PGND
SENSE1+
SENSE2+
SENSE1–
SENSE2–
VFB1
VFB2
ITH1
ITH2
20k
220pF TRACK/SS1 SGND TRACK/SS2
15k
0.1μF
0.1μF
4.7μF 0.1μF
220pF 15k
VIN 4V TO 36V 22μF 50V
7.2μH
0.015Ω
192.5k 20k
VOUT2 8.5V 3.5A
150μF
38261 TA01
EFFICIENCY (%)
POWER LOSS (mW)
Efficiency and Power Loss vs Load Current
100
10000
90
80
1000
70
60
100
50
40
10
30
20
1
10
0 0.00001 0.0001 0.001
FIGURE 13 CIRCUIT 0.1
0.01 0.1 1 10
OUTPUT CURRENT (A)
38261 TA01b
38261fb
1
LTC3826-1
ABSOLUTE MAXIMUM RATINGS
(Note 1)
Input Supply Voltage (VIN) ......................... 36V to –0.3V Topside Driver Voltages
BOOST1, BOOST2.................................. 42V to –0.3V Switch Voltage (SW1, SW2) ......................... 36V to –5V (BOOST1-SW1), (BOOST2-SW2) ............. 8.5V to –0.3V RUN1, RUN2 ............................................... 7V to –0.3V SENSE1+, SENSE2+, SENSE1–, SENSE2– Voltages ..................................... 11V to –0.3V PLLIN/MODE, PLLLPF, TRACK/SS1, TRACK/SS2
Voltages ........................................... INTVCC to –0.3V EXTVCC ...................................................... 10V to –0.3V ITH1, ITH2, VFB1, VFB2 Voltages ................. 2.7V to –0.3V PGOOD1 Voltage....................................... 8.5V to –0.3V Peak Output Current <10μs (TG1, TG2, BG1, BG2).....3A Operating Temperature Range (Note 2).... –40°C to 85°C Junction Temperature (Note 3) ............................. 125°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C
PIN CONFIGURATION
TOP VIEW
ITH1 1 VFB1 2 SENSE1+ 3 SENSE1– 4 PLLLPF 5 PLLIN/MODE 6 SGND 7 RUN1 8 RUN2 9 SENSE2– 10 SENSE2+ 11 VFB2 12 ITH2 13 TRACK/SS2 14
28 TRACK/SS1 27 PGOOD1 26 TG1 25 SW1 24 BOOST1 23 BG1 22 VIN 21 PGND 20 EXTVCC 19 INTVCC 18 BG2 17 BOOST2 16 SW2 15 TG2
G PACKAGE 28-LEAD PLASTIC SSOP TJMAX = 125°C, QJA = 95°C/W
ORDER INFORMATION
LEAD FREE FINISH LTC3826EG-1#PBF
TAPE AND REEL LTC3826EG-1#TRPBF
PART MARKING LTC3826EG-1
PACKAGE DESCRIPTION 28-Lead Plastic SSOP
LTC3826IG-1#PBF
LTC3826IG-1#TRPBF LTC3826IG-1
28-Lead Plastic SSOP
LEAD BASED FINISH LTC3826EG-1
TAPE AND REEL LTC3826EG-1#TR
PART MARKING LTC3826EG-1
PACKAGE DESCRIPTION 28-Lead Plastic SSOP
LTC3826IG-1
LTC3826IG-1#TR
.