LTC3828_15 Datasheet, PDF (1/32 Pages) Linear Technology – Dual, 2-Phase Step-Down Controller with Tracking

FEATURES
n _{Dual, 180° Phased Controllers Reduce Required}
Input Capacitance and Power Supply Induced Noise
n _{Tracking for Both Outputs}
n _{Constant Frequency Current Mode Control}
n _{Wide VIN Range: 4.5V to 28V Operation}
n _{Power Good Output Voltage Indicator}
n _{Adjustable Soft-Start Current Ramping}
n _{Foldback Output Current Limiting–}
Disabled at Start-Up
n _{No Reverse Current During Soft-Start Interval}
n _{Clock Output for 3-, 4-, 6-Phase Operation}
n _{Dual N-Channel MOSFET Synchronous Drive}
n _{±1% Output Voltage Accuracy}
n _{Phase-Lockable Fixed Frequency 260kHz to 550kHz}
n _OPTI-LOOP^® _{Compensation Minimizes COUT}
n _{Very Low Dropout Operation: 99% Duty Cycle}
n _{Output Overvoltage Protection}
n _{Small 28-Lead SSOP and 5mm × 5mm QFN}
Packages
APPLICATIONS
n _{Telecom Infrastructure}
n _{ASIC Power Supply}
n _{Industry Equipment}
LTC3828
Dual, 2-Phase Step-Down
Controller with Tracking
DESCRIPTION
The LTC^®3828 is a dual high performance step-down
switching regulator controller that drives all N-channel
synchronous power MOSFET stages. A constant frequency
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 battery 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.
L, LT, LTC, LTM, 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 APPLICATION
High Efficiency Dual 2.5V/3.3V Step-Down Converter with Tracking
3.2μH
+
4.7μF
0.1μF
V_IN PGOOD INTV_CC
TG1
TG2
BOOST1
BOOST2
SW1
SW2
LTC3828
BG1
BG2
1μF
CERAMIC
0.1μF
4.5V TO 28V
22μF
50V
CERAMIC
3.2μH
500kHz FCB/PLLIN
PGND
0.01Ω
3.3V
5A
+
63.4k 1%
47μF
4V
SP
63.4k 1%
20k
1% 20k
1%
SENSE1⁺
SENSE2⁺
1000pF
SENSE1^–
V_OSENSE1
SENSE2^–
V_OSENSE2
TRCKSS2
I_TH1
TRCKSS1
I_TH2
220pF RUN1 _SGND RUN2
15k
220pF
15k
1000pF
0.01Ω
TRCKSS1
42.5k
1%
20k
1%
0.1μF
2.5V
5A
+ 56μF
4V
SP
3828 TA01
3828fc
1