Datasheet LTC3425 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | 5A, 8MHz, 4-Phase Synchronous Step-Up DC/DC Converter |
| Pages / Page | 24 / 9 — PI FU CTIO S. ILIM (Pin 27):. SYNCIN (Pin 30):. SHDN (Pin 31):. RT (Pin … |
| File Format / Size | PDF / 284 Kb |
| Document Language | English |
PI FU CTIO S. ILIM (Pin 27):. SYNCIN (Pin 30):. SHDN (Pin 31):. RT (Pin 28):. SS (Pin 32):. IN (Pin 29):. Exposed Pad (Pin 33):
Model Line for this Datasheet
Text Version of Document
LTC3425
U U U PI FU CTIO S ILIM (Pin 27):
Current Limit Adjust Pin. Connect a resistor
SYNCIN (Pin 30):
Oscillator Synchronization Pin. A clock from ILIM to SGND to set the peak current limit threshold pulse width of 100ns minimum is required to synchronize for the N-channel MOSFETs, according to the formula the internal oscillator. If not used, SYNCIN should be (note that this is the peak current in each inductor): grounded. The typical logic threshold for this input is: V I OUT LIM = 130 R 2 where I is in Amps and R is in kΩ. Do not use values less The SYNCIN is ignored in Burst Mode operation. than 75k.
SHDN (Pin 31):
Shutdown Pin. Grounding SHDN (or
RT (Pin 28):
Connect a resistor from RT to SGND (or SGND pulling it below 0.25V) shuts down the IC. Pull pin up to plane) to program the oscillator frequency, according to ≥1V to enable. Once enabled, the pin only needs to be the formula: ≥0.65V. 60
SS (Pin 32):
Soft-Start pin. Connect a capacitor from this fOSC = pin to ground to set the soft-start time, according to the RT formula: f 15 f OSC SWITCH = = 4 R t(ms) = CSS (µF) • 320 T The nominal soft-start charging current is 2.5µA. The where fOSC is in MHz and RT is in kΩ. active range of SS is from 0.8V to 1.6V. Note that this is the
V
rise time of SS. The actual rise time of V
IN (Pin 29):
Input Supply Pin. Connect this to the input OUT will be a supply and decouple with 1µF minimum low ESR function of load and output capacitance. ceramic capacitor.
Exposed Pad (Pin 33):
Additional Power Ground for the IC. Connect directly to the power ground plane.
OPERATING MODE BURST PIN CCM PIN
Automatic Burst (Operating Mode is Load Dependent) RC Network to Ground Low Forced Burst Low Low Forced Fixed Frequency with Pulse Skipping at Light Load High Low Forced Fixed Frequency, Low Noise (No Pulse Skipping) High High 3425f 9
U U U PI FU CTIO S ILIM (Pin 27):
Current Limit Adjust Pin. Connect a resistor
SYNCIN (Pin 30):
Oscillator Synchronization Pin. A clock from ILIM to SGND to set the peak current limit threshold pulse width of 100ns minimum is required to synchronize for the N-channel MOSFETs, according to the formula the internal oscillator. If not used, SYNCIN should be (note that this is the peak current in each inductor): grounded. The typical logic threshold for this input is: V I OUT LIM = 130 R 2 where I is in Amps and R is in kΩ. Do not use values less The SYNCIN is ignored in Burst Mode operation. than 75k.
SHDN (Pin 31):
Shutdown Pin. Grounding SHDN (or
RT (Pin 28):
Connect a resistor from RT to SGND (or SGND pulling it below 0.25V) shuts down the IC. Pull pin up to plane) to program the oscillator frequency, according to ≥1V to enable. Once enabled, the pin only needs to be the formula: ≥0.65V. 60
SS (Pin 32):
Soft-Start pin. Connect a capacitor from this fOSC = pin to ground to set the soft-start time, according to the RT formula: f 15 f OSC SWITCH = = 4 R t(ms) = CSS (µF) • 320 T The nominal soft-start charging current is 2.5µA. The where fOSC is in MHz and RT is in kΩ. active range of SS is from 0.8V to 1.6V. Note that this is the
V
rise time of SS. The actual rise time of V
IN (Pin 29):
Input Supply Pin. Connect this to the input OUT will be a supply and decouple with 1µF minimum low ESR function of load and output capacitance. ceramic capacitor.
Exposed Pad (Pin 33):
Additional Power Ground for the IC. Connect directly to the power ground plane.
OPERATING MODE BURST PIN CCM PIN
Automatic Burst (Operating Mode is Load Dependent) RC Network to Ground Low Forced Burst Low Low Forced Fixed Frequency with Pulse Skipping at Light Load High Low Forced Fixed Frequency, Low Noise (No Pulse Skipping) High High 3425f 9
