LTC3828 Datasheet, PDF (1/32 Pages) Linear Technology – Dual 2-Phase Step-Down Controller with Tracking

FEATURES
■ _{Dual, 180° Phased Controllers Reduce Required}
Input Capacitance and Power Supply Induced Noise
■ _{Tracking for Both Outputs}
■ _{Constant Frequency Current Mode Control}
■ _{Wide VIN Range: 4.5V to 28V Operation}
■ _{Power Good Output Voltage Indicator}
■ _{Adjustable Soft-Start Current Ramping}
■ _{Foldback Output Current Limiting–}
Disabled at Start-Up
■ _{No Reverse Current During Soft-Start Interval}
■ _{Clock Output for 3-, 4-, 6-Phase Operation}
■ _{Dual N-Channel MOSFET Synchronous Drive}
■ _{±1% Output Voltage Accuracy}
■ _{Phase-Lockable Fixed Frequency 260kHz to 550kHz}
■ _OPTI-LOOP^® _{Compensation Minimizes COUT}
■ _{Very Low Dropout Operation: 99% Duty Cycle}
■ _{Output Overvoltage Protection}
■ _{Small 28-Lead SSOP and 5mm × 5mm QFN}
Packages
U
APPLICATIO S
■ _{Telecom Infrastructure}
■ _{ASIC Power Supply}
■ _{Industry Equipment}
LTC3828
Dual, 2-Phase Step-Down
Controller with Tracking
DESCRIPTIO
The LTC^®3828 is a dual high performance step-down
switching regulator controller that drives all N-channel
synchronous power MOSFET stages. A constant fre-
quency current mode architecture allows for a phase-
lockable frequency of up to 550kHz. The TRCKSS pin
provides both soft-start and tracking functions. Multiple
LTC3828s can be daisy-chained in applications requiring
more than two voltages to be tracked.
OPTI-LOOP compensation allows the transient response
to be optimized over a wide range of output capacitance and
ESR values. The precision 0.8V reference and power good
output indicator are compatible with a wide 4.5V to 28V
(30V maximum) input supply range, encompassing all bat-
tery chemistries.
The RUN pins control their respective channels indepen-
dently. The FCB/PLLIN pin selects among Burst Mode^®
operation, skip-cycle mode and continuous current mode.
Current foldback limits MOSFET dissipation during short-
circuit conditions. Reverse current and current foldback
functions are disabled during soft-start.
, LTC and LT 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, 5705919, 5929620, 6144194, 6177787,
6304066, 6580258
TYPICAL APPLICATIO
High Efficiency Dual 2.5V/3.3V Step-Down Converter with Tracking
+
4.7µF
V_IN PGOOD INTV_CC
TG1
TG2
1µF
CERAMIC
4.5V TO 28V
22µF
50V
CERAMIC
3.2µH
0.1µF
BOOST1
BOOST2
SW1
SW2
LTC3828
BG1
BG2
0.1µF
3.2µH
500kHz FCB/PLLIN
PGND
SENSE1⁺
SENSE2⁺
0.01Ω
1000pF
1000pF
0.01Ω
SENSE1^–
SENSE2^–
3.3V
5A
+
63.4k 1%
47µF
4V
SP
63.4k 1%
20k
1% 20k
1%
0.1µF
220pF
V_OSENSE1
TRCKSS2
I_TH1
V_OSENSE2
TRCKSS1
I_TH2
RUN1 SGND RUN2
220pF
15k
15k
42.5k
2.5V
TRCKSS1
1%
5A
20k
1%
0.1µF
56µF
4V
SP
3828 TA01
3828f
1