Datasheet LTC3545, LTC3545-1 (Analog Devices)

LTC3545/LTC3545-1 Triple 800mA Synchronous Step-Down Regulator–2.25MHz
FEATURES DESCRIPTION
■
Three 800mA Outputs
The LTC®3545/LTC3545-1 are triple, high efficiency, ■
High Effi ciency: Up to 95%
monolithic synchronous buck regulators using a constant ■
2.25V to 5.5V Input Voltage Range
frequency, current mode architecture. The regulators op- ■
Low Ripple (<20mVP-P) Burst Mode
®
Operation
erate independently with separate run pins. The 2.25V to
IQ: 58μA
5.5V input voltage range makes the LTC3545/LTC3545-1 ■
2.25MHz Constant Frequency Operation or
well suited for single Li-Ion battery-powered applications. ■
Synchronizable to External 1MHz to 3MHz Clock
Low ripple pulse skip mode or high effi ciency Burst Mode ■
Power Good Indicators Ease Supply Sequencing
operation is externally selectable. PWM pulse skip mode ■ 0.6V Reference Allows Low Output Voltages operation provides very low output ripple voltage while ■ Current Mode Operation/Excellent Transient Response Burst Mode operation increases effi ciency at low output ■ Low Profi le 16-Lead 3mm × 3mm QFN Package loads.
APPLICATIONS
Switching frequency is internally set to 2.25MHz, or the switching frequency can be synchronized to an external ■ Smart Phones 1MHz to 3MHz clock. Power good indicators easily allow ■ Wireless and DSL Modems power on sequencing between the three regulators. ■ Digital Still Cameras ■ The internal synchronous switches increase effi ciency and Portable Instruments ■ eliminate external Schottky diodes. Low output voltages are Point of Load Regulation supported with the 0.6V feedback reference voltage. L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. Protected by U.S. Patents including 6580258, 5481178, 6127815, 6498466, 6611131. The LTC3545-1 replaces the SYNC/MODE function with a third PGOOD pin and forces Burst Mode operation.
TYPICAL APPLICATION High Effi ciency Triple Step-Down Converter with Power Sequencing Effi ciency and Loss vs Load Current
VIN 2.25V TO 5.5V 100 1 C5 C4 10μF 10μF 90 GNDA PGND 80 R8 R7 L2 0.1 500k 500k 1.5μH 70 VIN PVIN V RUN1 OUT2 SW2 LOSS (W) C7 1.2V 60 PGOOD1 20pF 50 0.01 RUN2 VFB2 40 R4 C2 PGOOD2 R3 EFFICIENCY (%) 226k 10μF 30 226k RUN3 LTC3545 0.001 20 VIN = 2.5V L1 SYNC/MODE L3 10 VIN = 3.6V 1.5μH 1.5μH VIN = 4.2V VOUT1 V 0 0.0001 SW1 OUT3 SW3 1.8V C6 C8 1.5V 0.0001 0.001 0.01 0.1 1 20pF 20pF LOAD CURRENT (A) C1 C3 V V 3545 TA01b T 10μF FB1 FB3 10μF A = 25°C V R2 OUT = 2V R1 GNDA PGND R6 R5 Burst Mode OPERATION 255k 511k 200k 301k fOSC = 2.25MHz 3545 TA01 SINGLE CHANNEL 35451fb 1