Datasheet LT3956 (Analog Devices) - 8
| Fabricante | Analog Devices |
| Descripción | 80VIN, 80VOUT Constant-Current, Constant-Voltage Converter |
| Páginas / Página | 20 / 8 — VREF:. SS:. PWM:. VMODE:. RT: |
| Formato / tamaño de archivo | PDF / 1.5 Mb |
| Idioma del documento | Inglés |
VREF:. SS:. PWM:. VMODE:. RT:
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LT3956 pin FuncTions
VREF:
Voltage Reference Output Pin (typically 2V). This high. When PWM input goes high again, the VMODE pin pin drives a resistor divider for the CTRL pin, either for will be updated. This pin may be used to report an open analog dimming or for temperature limit/compensation LED fault. Use a pull-up current less than 1mA. of LED load. Can supply up to 100μA.
SS:
Soft-Start Pin. This pin modulates oscil ator fre-
PWM:
A signal low turns off switcher, idles oscillator and quency and compensation pin voltage (VC) clamp. The disconnects VC pin from all internal loads. PWMOUT pin soft-start interval is set with an external capacitor. The follows PWM pin. PWM has an internal pull-down resistor. pin has a 10µA (typical) pul -up current source to an If not used, connect to INTVCC. internal 2.5V rail. The soft-start pin is reset to GND by
VMODE:
An open-collector pull-down on VMODE asserts an undervoltage condition (detected by EN/UVLO pin) if the FB input is greater than the FB regulation threshold or thermal limit. minus 50mV (typical). To function, the pin requires an
RT:
Switching Frequency Adjustment Pin. Set the fre- external pull-up resistor. When the PWM input is low quency using a resistor to GND (for resistor values, see and the DC/DC converter is idle, the VMODE condition is the Typical Performance curve or Table 1). Do not leave latched to the last valid state when the PWM input was the RT pin open. block DiagraM EN/UVLO – A6 FB VC PWMOUT PWM VIN – + SHDN 1.22V + 1.31V – LDO 2.1µA OVFB 1.25V COMPARATOR +A8 7.15V INTVCC + A5 g 10µA AT 1.25V – m FB = 1.25V SW SHORT-CIRCUIT DETECT SCILMB + 10µA + A10 SCILMB – 350mV – + g R Q m DRIVER ISN S + EAMP –A2 PWM 10µA AT ISP COMPARATOR 5k –A1 ISENSE A1+ = A1– + PGND CTRL A4 CTRL BUFFER – + 1.1V + Q2 –A3 VC RAMP GND GENERATOR SSCLAMP 20k 100kHz TO 1MHz OSCILLATOR VMODE FAULT 10µA 140µA – LOGIC 1.25V + V 1.2V 1mA (MAX) REF + – + FB TSD FREQ – 165°C PROG A7 170k + 2V SS RT 3956 BD 3956f Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration order information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Application Package Description Typical Application Related Parts
VREF:
Voltage Reference Output Pin (typically 2V). This high. When PWM input goes high again, the VMODE pin pin drives a resistor divider for the CTRL pin, either for will be updated. This pin may be used to report an open analog dimming or for temperature limit/compensation LED fault. Use a pull-up current less than 1mA. of LED load. Can supply up to 100μA.
SS:
Soft-Start Pin. This pin modulates oscil ator fre-
PWM:
A signal low turns off switcher, idles oscillator and quency and compensation pin voltage (VC) clamp. The disconnects VC pin from all internal loads. PWMOUT pin soft-start interval is set with an external capacitor. The follows PWM pin. PWM has an internal pull-down resistor. pin has a 10µA (typical) pul -up current source to an If not used, connect to INTVCC. internal 2.5V rail. The soft-start pin is reset to GND by
VMODE:
An open-collector pull-down on VMODE asserts an undervoltage condition (detected by EN/UVLO pin) if the FB input is greater than the FB regulation threshold or thermal limit. minus 50mV (typical). To function, the pin requires an
RT:
Switching Frequency Adjustment Pin. Set the fre- external pull-up resistor. When the PWM input is low quency using a resistor to GND (for resistor values, see and the DC/DC converter is idle, the VMODE condition is the Typical Performance curve or Table 1). Do not leave latched to the last valid state when the PWM input was the RT pin open. block DiagraM EN/UVLO – A6 FB VC PWMOUT PWM VIN – + SHDN 1.22V + 1.31V – LDO 2.1µA OVFB 1.25V COMPARATOR +A8 7.15V INTVCC + A5 g 10µA AT 1.25V – m FB = 1.25V SW SHORT-CIRCUIT DETECT SCILMB + 10µA + A10 SCILMB – 350mV – + g R Q m DRIVER ISN S + EAMP –A2 PWM 10µA AT ISP COMPARATOR 5k –A1 ISENSE A1+ = A1– + PGND CTRL A4 CTRL BUFFER – + 1.1V + Q2 –A3 VC RAMP GND GENERATOR SSCLAMP 20k 100kHz TO 1MHz OSCILLATOR VMODE FAULT 10µA 140µA – LOGIC 1.25V + V 1.2V 1mA (MAX) REF + – + FB TSD FREQ – 165°C PROG A7 170k + 2V SS RT 3956 BD 3956f Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration order information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Application Package Description Typical Application Related Parts