LT8640_15 Datasheet, PDF (1/26 Pages) Linear Technology – 42V, 5A Synchronous Step-Down Silent Switcher with 2.5A Quiescent Current

LT8640
42V, 5A Synchronous
Step-Down Silent Switcher
with 2.5µA Quiescent Current
FEATURES
DESCRIPTION
nn _{Silent Switcher}^® _Architecture
nn _{Ultralow EMI/EMC Emissions}
nn _{Spread Spectrum Frequency Modulation}
nn _{High Efficiency at High Frequency}
nn _{Up to 96% Efficiency at 1MHz}
nn _{Up to 95% Efficiency at 2MHz}
nn _{Wide Input Voltage Range: 3.4V to 42V}
nn _{5A Maximum Continuous Output, 7A Peak}
Transient Output
nn _{Ultralow Quiescent Current Burst Mode}^® _Operation
nn _{2.5μA IQ Regulating 12VIN to 3.3VOUT}
nn _{Output Ripple < 10mVP-P}
nn _{Fast Minimum Switch-On Time: 40ns}
nn _{Low Dropout Under All Conditions: 100mV at 1A}
nn _{Safely Tolerates Inductor Saturation in Overload}
nn _{Adjustable and Synchronizable: 200kHz to 3MHz}
nn _{Peak Current Mode Operation}
nn _{Output Soft-Start and Tracking}
nn _{Small 18-Lead 3mm × 4mm QFN}
APPLICATIONS
nn _{Automotive and Industrial Supplies}
nn _{General Purpose Step-Down}
nn _{GSM Power Supplies}
The LT^®8640 step-down regulator features Silent Switcher
architecture designed to minimize EMI/EMC emissions
while delivering high efficiency at frequencies up to 3MHz.
Assembled in a 3mm × 4mm QFN, the monolithic construc-
tion with integrated power switches and inclusion of all
necessary circuitry yields a solution with a minimal PCB
footprint. An ultralow 2.5µA quiescent current—with the
output in full regulation—enables applications requiring
highest efficiency at very small load currents. Transient
response remains excellent and output voltage ripple is
below 10mV_P-P at any load, from zero to full current.
The LT8640 allows high V_IN to low V_OUT conversion at
high frequency with a fast minimum top switch on-time of
40ns. Operation is safe in overload even with a saturated
inductor.
Essential features are included and easy to use: An
open-drain PG pin signals when the output is in regula-
tion. The SYNC/MODE pin selects between Burst Mode,
pulse-skipping, or spread spectrum mode, and also al-
lows synchronization to an external clock. Soft-start and
tracking functionality is accessed via the TR/SS pin. An
accurate enable threshold can be set using the EN/UV pin
and a resistor at the RT pin programs switch frequency.
L, LT, LTC, LTM, Linear Technology, the Linear logo, Silent Switcher and Burst Mode are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
TYPICAL APPLICATION
V_IN
5.5V TO 42V
5V 5A Step-Down Converter
4.7µF
1µF
10nF
1µF
41.2k
V_IN1 ^EN/UV V_IN2
GND1
GND2
LT8640
PG
BST
SYNC/MODE SW
TR/SS
BIAS
INTV_CC
FB
RT
GND
1µF
0.1µF 3.3µH
V_OUT
5V
5A
4.7pF
1M
47µF
243k
f_SW = 1MHz
8640 TA01a
12V_IN to 5V_OUT Efficiency
100
3.00
95
2.63
90
EFFICIENCY
2.25
85
1.88
80
1.50
75
1.13
POWER LOSS
70
0.75
65
60
0.5
1MHz, L = 3.3µH
2MHz, L = 2.2µH ^0.38
3MHz, L = 1µH
0
1 1.5 2 2.5 3 3.5 4 4.5 5
LOAD CURRENT (A)
8640 TA01b
For more information www.linear.com/LT8640
8640f
1