Datasheet
LMR70503
U1
GND
SW
VOUT
VIN
EN
Cin2
(NC)
Co1
D1
VOUT
L1
FB
VREF
R1
Rt
Cff
Co2
R7
R6
J1
R2 R3 R4 R5
Cin1
SW
EN
GND
VIN
A1
A2
B2
B1
D1D2
C1
C2
LMR70503 Demo Board Schematic
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2 LMR70503 Demo Board Schematic
Figure 2. LMR70503 Demo Board Schematic
3 LMR70503 Features
• Tiny 8-Bump DSBGA Package: 0.84 mm × 1.615 mm × 0.6 mm
• 2.8 V to 5.5 V Input Voltage Range
• Adjustable Output Voltage: -0.9 V to -5.5 V
• 320 mA Switch Current Limit
• 500 kHz Minimum Switching Frequency
• Ground Referred Enable Input
• Under Voltage Lock Out (UVLO)
• No External Compensation
• Internal Soft Start
• 1 μA Shutdown Supply Current
• WEBENCH
®
Enabled
4 Selecting the Output Voltage
One of five output voltages can be selected by J1. The default setting is J1 open and the output voltage is
-5.0 V, set by resistor divider R1 and R
t
:
V
OUT
= – V
REF
* R1 / R
t
(1)
When one of the four positions of J1 is connected, the resistor connected between this position and V
OUT
is paralleled with R1 to provide a lower magnitude output voltage. Output voltages of -3.3 V, -2.5 V, -1.5 V
and -0.9 V can be selected by J1, as shown in Figure 1 and Figure 2.
Output voltage other than these five preset values can be achieved by replacing R1 and keep J1 open:
R1 = R
t
* |V
OUT
| / V
REF
(2)
where V
REF
is typically 1.19 Vand R
t
is 100 kΩ. R
t
can be selected between 20 kΩ and 100 kΩ.
2
AN-2264 LMR70503 Demo Board SNVU155A–June 2012–Revised April 2013
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