Datasheet LTC3527, LTC3527-1 (Analog Devices) - 8

LTC3527/LTC3527-1
PIN FUNCTIONS SHDN1 (Pin 1):
Boost Converter 1 Logic-Controlled MOSFET. Driver bias is derived from VOUT2. PCB trace Shutdown Input. There is an internal 4MΩ pull-down on length from VOUT2 to the output fi lter capacitor(s) should this pin. be as short and wide as possible. • SHDN1 = High: Normal free running operation, 1.2MHz/
FSEL (Pin 10):
Logic-Controlled Frequency Select 2.2MHz typical operating frequency. Input. • SHDN1 = Low: Shutdown, quiescent current < 2μA. • FSEL = High: 2.2MHz operation Note: Both converters must be shut down together to • FSEL = Low: 1.2MHz operation achieve < 2μA quiescent current.
FB2 (Pin 11):
Boost Converter 2 Feedback Input to the
FB1 (Pin 2):
Boost Converter 1 Feedback Input to the gm gm Error Amplifi er. Connect resistor divider tap to this Error Amplifi er. Connect resistor divider tap to this pin. The pin. The output voltage can be adjusted from 1.6V to output voltage can be adjusted from 1.6V to 5.25V by: 5.25V by: ⎡ R1⎤ ⎡ R3 ⎤ V = . V • + S ( ee Block Diagram OUT1 1 20 1 ) V = . V • + S ( ee Block Diagram OUT2 1 20 1 ) R2 ⎣⎢ ⎦⎥ R4 ⎣⎢ ⎦⎥
MODE (Pin 3):
Logic-Controlled Mode Input for Both
SHDN2 (Pin 12):
Boost Converter 2 Logic-Controlled Boost Converters. Shutdown Input. There is an internal 4MΩ pull-down on • MODE = High: Fixed frequency operation this pin. • MODE = Low: Automatic Burst Mode operation • SHDN2 = High: Normal free-running operation, 1.2MHz/2.2MHz typical operating frequency. MODE pin must be 1V or greater to ensure fi xed frequency over all operating conditions. • SHDN2 = Low: Shutdown, quiescent current < 2μA.
V
Note: Both converters must be shut down together to
OUT1 (Pin 5):
Boost Converter 1 Output Voltage Sense Input and Drain of the Internal Synchronous Rectifi er achieve < 2μA quiescent current. MOSFET. Driver bias is derived from VOUT1. PCB trace
PGOOD2 (Pin 13):
Boost Converter 2 Power Good Com- length from VOUT1 to the output fi lter capacitor(s) should parator Output. This open-drain output is low when VFB be as short and wide as possible. is 9% below its regulation voltage.
SW1 (Pin 6):
Boost Converter 1 Switch Pin. Connect the
GND (Pin 14):
Signal Ground. This pin is used as a inductor between SW1 and VIN1. Keep these PCB trace ground reference for the internal circuitry of the LTC3527/ lengths as short and wide as possible to reduce EMI and LTC3527-1. voltage overshoot. If the inductor current falls to zero or SHDN1 is low, an internal 100Ω anti-ringing switch is
VIN, VIN1, VIN2 (Pins 15, 4, 9):
Battery Input Voltage. See connected from SW1 to V Operation section for more information. IN1 to minimize EMI.
SW2 (Pin 7):
Boost Converter 2 Switch Pin. Connect the
PGOOD1 (Pin 16)
Boost Converter 1 Power Good Com- inductor between SW2 and V parator Output. This open-drain output is low when V IN2. Keep these PCB trace FB lengths as short and wide as possible to reduce EMI and is 9% below its regulation voltage. voltage overshoot. If the inductor current falls to zero or
PGND (Exposed Pad Pin 17):
Backplane. The exposed pad SHDN2 is low, an internal 100Ω anti-ringing switch is is PGND and must be soldered to the PCB ground plane. connected from SW2 to VIN2 to minimize EMI. It serves as the power ground connection for VOUT1 and
VOUT2 (Pin 8):
Boost Converter 2 Output Voltage Sense VOUT2, and as a means of conducting heat away from the Input and Drain of the Internal Synchronous Rectifi er package. 35271fc 8