2
AN1396.0
July 31, 2008
Take Channel-1 as an example, once the value of R
OCSET
is calculated, follow the following procedure to configure the
resistor current sense circuit:
Step 1:
Open the “DCR SENSE” solder bridge and
connect the “RESISTOR SENSE” solder bridge
on the PCB bottom layer;
Step 2:
Remove R
7
(R
22
for Channel 2);
Step 3:
Replace R
3
(R
25
for Channel 2) with R
SENSE
;
Step 4:
R
eplace C
6
(C
25
for Channel 2) with R
OCSET;
Step 5:
R
eplace replace R
19
(R
18
for Channel 2) with
R
OCSET.
Dynamic Load Generator
The evaluation board provides each PWM channel an
on-board dynamic load generator for evaluating the
transient-load response, which are controlled by SW1 and
SW2 respectively. The dynamic load generator applies a
300µs pulse load across V
OUT
and GND. The transient load
slew-rate can be trimmed by adjusting the resistors R
34
, R
40
for the rising edge, and R
38
, R
39
for the falling edge. +12V
power supply is needed to power the dynamic load
generator.
Connections and Test Points
The following table describes the function and operation of the evaluation boards.
NUMBER
NAME
FUNCTION/OPERATION
INTERFACES AND CONNECTIONS
TP3
VBAT
V
IN
positive power input
TP4
GND
V
IN
return power input
TP1
VOUT1
Channel-1 positive power output
TP2
GND
Channel-1 return power output
TP11
VOUT2
Channel-2 positive power output
TP12
GND
Channel-2 return power output
TP20
+12V
+12V positive power input, used for the power supply of the on-board dynamic-load generator
TP19
GND
+12V return power input
TEST POINTS
J1
PHASE2
Scope-probe socket for measuring Channel-2 phase node
J3
PHASE1
Scope-probe socket for measuring Channel-1 phase node
J2
VOUT1
Scope-probe socket for measuring Channel-1 output
J5
VOUT2
Scope-probe socket for measuring Channel-2 output
J4
FLOAT_FCCM
Remove the jumper will float the FCCM pin
J6
FLOAT_EN1
Remove the jumper will float the EN1 pin
J7
FLOAT_EN2
Remove the jumper will float the EN2 pin
TP17
EN1
Test point of EN1 pin
TP8
EN2
Test point of EN2 pin
TP9
LDO3EN
Test point of LDO3EN pin
TP10
FCCM
Test point of FCCM pin
POWER-GOOD INDICATORS
TP13
PGOOD1
Test point of PGOOD1 pin
TP5
PGOOD2
Test point of PGOOD2 pin
D1
Channel-1 Power-Good indicator. Green when VOUT1 is in regulation.
D2
Channel-2 Power-Good indicator. Green when VOUT2 is in regulation.
LINEAR REGULATORS
TP14
LDO5
LDO5 linear regulator positive power output
TP15
GND
LDO5 linear regulator return power output
TP16
LDO3IN
Input of LDO3 linear regulator. Connect to connected to a voltage greater than the LDO3 set point plus the dropout
voltage.
TP18
LDO3FB
LDO3 linear regulator output voltage feedback test point
TP6
LDO3
LDO3 linear regulator positive power output
TP7
GND
LDO3 linear regulator return power output
Application Note 1396
