LTC1704EGN Datasheet, PDF (1/28 Pages) Linear Technology – 550kHz Synchronous Switching Regulator Controller Plus Linear Regulator Controller

LTC1704/LTC1704B
550kHz Synchronous
Switching Regulator Controller
Plus Linear Regulator Controller
FEATURES
s _{Dual Regulated Outputs: One Switching Regulator}
and One Linear Regulator
s _{Excellent DC Accuracy: ±1.5% for Switcher}
and ±2% for Linear Regulator
s _{External N-Channel MOSFET Architecture}
s _{No External Current Sense Resistor Required}
s _{Burst Mode}^® _{Operation at Light Load (LTC1704)}
s _{Continuous Switching at Light Load (LTC1704B)}
s _{Linear Regulator with Programmable Current Limit}
s _{Linear Regulator with Programmable Start-Up Delay}
s _{Low Shutdown Current: <150µA}
s _{High Efficiency Over Wide Load Current Range}
s _{PGOOD Flag Monitors Both Outputs}
s _{Small 16-Pin Narrow SSOP Package}
U
APPLICATIO S
s _{Multiple Logic Supply Generator}
s _{Distributed Power Applications}
s _{High Efficiency Power Conversion}
, LTC and LT are registered trademarks of Linear Technology Corporation.
Burst Mode is a registered trademark of Linear Technology Corporation.
DESCRIPTIO
The LTC^®1704/LTC1704B include a high power synchro-
nous switching regulator controller plus a linear regulator
controller. The switching regulator controller is designed
to drive a pair of N-channel MOSFETs in a voltage mode,
synchronous buck configuration to provide the main sup-
ply. The constant frequency, true PWM architecture
switches at 550kHz, minimizing external component size,
cost and optimizing load transient performance. The
LTC1704 features automatic transition to power saving
Burst Mode operation at light loads. The LTC1704B does
not shift into Burst Mode operation at light loads, eliminat-
ing low frequency output ripple at the expense of light load
efficiency. The linear regulator controller is designed to
drive an external NPN power transistor to provide up to 2A
of current to an auxiliary load.
The LTC1704/LTC1704B deliver better than ±1.5% DC
accuracy at the switcher outputs and ±2% at the linear
regulator outputs. High performance feedback loops allow
the circuit to keep total output regulation within ±5%
under all transient conditions. An open-drain PGOOD
output indicates when both outputs are within ±10% of
their regulated values.
TYPICAL APPLICATIO
V_IN
5V
C_{IN +}
330µF
10V
×3
V_OUTSW
1.8V
15A
C_{OUTSW +}
180µF
4V
×6
10k
8.06k
5V to 1.8V/15A and 1.5V/2A Application
10Ω
1µF
L1 ^QTA
0.68µH
QBB
MBR0520LT1
+
10µF
5k
16 15
11
C_CP
1µF BOOST PV_CC V_CC
QTB
1
12
TG
PGOOD
2
SW
10
REGILM
14
4
QBA
BG
RUN/SS
13.7k ₃
LTC1704
8
I_MAX
GND
1800pF ^1.8k
1800pF _11k
13
PGND
6
FB
330pF
5
COMP
C_IN: KEMET T510X337K010AS
C_OUTSW: PANASONIC EEFUE0G181R
L: SUMIDA CEP125-4712-T007
QTA, QTB, QBA, QBB: FAIRCHILD FDS6670A
7
REGDR
9
REGFB
+
470k
10µF
0.1µF
1000pF
ON SEMI
D44H11
V_OUTSW
698Ω ₊
806Ω
100µF
TANT
V_OUTREG
1.5V
2A
1704 TA01
Switcher Efficiency
100
90
80
70
60
V_IN = 5V
V_OUTSW = 1.8V
T_A = 25°C
QT = QB = 2xFDS6670A
50
0
3
6
9
I_LOAD (A)
12
15
1704 G04
1704bfa
1