LTC3769_15 Datasheet, PDF (8/32 Pages) Linear Technology – 60V Low IQ Synchronous Boost Controller

LTC3769
Typical Performance Characteristics T_A = 25°C unless otherwise noted.
Maximum Current Sense
Threshold vs Duty Cycle
120
100 ^{ILIM = INTVCC}
80 ILIM = FLOAT
60
I_LIM = GND
40
20
Charge Pump Charging Current
vs Operating Frequency
80
T = –60°C
70
60
T = –45°C
50
T = 25°C
40
T = 130°C
30
T = 155°C
20
10
Charge Pump Charging Current
vs Switch Voltage
70
FREQ = GND
60
FREQ = INTV_CC
50
40
30
20
10
0
0 10 20 30 40 50 60 70 80 90 100
DUTY CYCLE (%)
3769 G25
0
50 150 250 350 450 550 650 750
OPERATING FREQUENCY (kHz)
3769 G26
0
5 15 25 35 45 55 65
SWITCH VOLTAGE (V)
3769 G27
Pin Functions (QFN/TSSOP)
VBIAS (Pin 1/Pin 19): Main Supply Pin. It is normally
tied to the input supply V_IN or to the output of the boost
converter. A bypass capacitor should be tied between this
pin and the signal ground pin. The operating voltage range
on this pin is 4.5V to 60V (65V abs max).
PGOOD (Pin 2/Pin 20): Power Good Indicator. Open-drain
logic output that is pulled to ground when the output volt-
age is more than ±10% away from the regulated output
voltage. To avoid false trips the output voltage must be
outside the range for 45μs before this output is activated.
ILIM (Pin 3/Pin 1): Current Comparator Sense Voltage
Range Input. This pin is used to set the peak current
sense voltage in the current comparator. Connect this
pin to SGND, leave floating or connect to INTV_CC to set
the peak current sense voltage to 50mV, 75mV or 100mV,
respectively.
INTV_CC (Pins 5, 22/Pins 2, 17): Output of Internal 5.4V LDO.
Power supply for control circuits and gate drivers. De-
couple pin 22/17 to GND with a minimum 4.7μF low ESR
ceramic capacitor. Connect pin 5/2 to pin 22/17 with a
trace on the printed circuit board.
FREQ (Pin 7/Pin 3): Frequency Control Pin for the Internal
VCO. Connecting the pin to GND forces the VCO to a fixed
low frequency of 350kHz. Connecting the pin to INTV_CC
forces the VCO to a fixed high frequency of 535kHz. The
frequency can be programmed from 50kHz to 900kHz
by connecting a resistor from the FREQ pin to GND. The
resistor and an internal 20μA source current create a volt-
age used by the internal oscillator to set the frequency.
Alternatively, this pin can be driven with a DC voltage to
vary the frequency of the internal oscillator.
GND (Pin 8, 10, 24, Exposed Pad Pin 25/ Pin 4, Exposed
Pad Pin 21): Ground. All ground pins must be connected
and the exposed pad must be soldered to the PCB for
rated electrical and thermal performance.
PLLIN/MODE (Pin 9/Pin 5): External Synchronization
Input to Phase Detector and Forced Continuous Mode
Input. When an external clock is applied to this pin, the
phase-locked loop will force the rising edge of BG to be
synchronized with the rising edge of the external clock.
When an external clock is applied to this pin, the OVMODE
pin is used to determine how the LTC3769 operates at light
load. When not synchronizing to an external clock, this
3769f
8
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