LTC3523-2_15 Datasheet, PDF (5/16 Pages) Linear Technology – Synchronous 600mA Step-Up and 400mA Step-Down DC/DC Converters

LTC3523/LTC3523-2
TYPICAL PERFORMANCE CHARACTERISTICS (T_A = 25°C unless otherwise noted)
Normalized R_DS(ON) vs
Temperature
1.3
1.2
1.1
1.0
PMOS
0.9
NMOS
0.8
0.7
0.6
0.5
–45 –25
–5 15 35 55
TEMPERATURE (°C)
75
3523 G10
Step-Up No-Load Input Current
vs V_IN
500
450
400
V_OUT = 5V
350
300
250
200
V_OUT = 3.3V
150
100
50 _{VOUT = 2.8V}
0
1.5 2 2.5 3 3.5 4 4.5 5
INPUT VOLTAGE (V)
3523 G11
Mode Transition Response
V_{OUT_BST}
50mV/DIV
V_{OUT_BCK}
20mV/DIV
MODE
2V/DIV
V_OUT1 = 3.3V 200μs/DIV
V_OUT2 = 1.2V
V_IN = 2.4V
I_OUT1 = 20mA
I_OUT2 = 25mA
C_OUT1 = C_OUT2 = 10μF
L1 = L2 = 4.7μH
Maximum I_OUT vs V_IN for the
Step-Up Converter
500
450
V_OUT = 3.3V
400 ^{VOUT = 2.5V}
V_OUT = 5V
350
300
250
200
150
100
50
0
1
2
3
4
5
INPUT VOLTAGE (V)
3523 G13
Maximum I_OUT vs V_IN for the
Step-Down Converter
450
V_OUT = 1.8V
400
350 _{VOUT = 1.2V}
V_OUT = 2.5V
300
250
200
150
100
50
0
1 1.5 2 2.5 3 3.5 4 4.5 5
INPUT VOLTAGE (V)
3523 G14
3523 G12
PIN FUNCTIONS
FB1 (Pin 1): Step-Up Converter Feedback Input to the Er-
ror Amplifier. Connect resistor divider tap to this pin. The
output voltage can be adjusted from 1.8V to 5.25V by:
V_OUT(STEP-UP)
=
1.2V
•
⎛⎝⎜₁₊
R1⎞
R2⎠⎟
See Block Diagram.
V_IN1 (Pin 2): Step-Up Converter Power Voltage Input. This
pin can be connected to a different supply than V_IN2. This
pin must be connected to a valid supply voltage.
PGOOD1 (Pin 3): Step-Up Converter Power Good Com-
parator Output. This open-drain output is pulled low when
V_FB1 < –9% of its regulation voltage.
V_OUT (Pin 4): Step-Up Converter Output Voltage Sense Input
and Drain of the Internal Synchronous Rectifier MOSFET.
Driver bias is derived from V_OUT. PCB trace length from
V_OUT to the output filter capacitor(s) should be as short
and wide as possible.
3523fb
5