MAX16823EVKIT データシートの表示（PDF） - Maxim Integrated
部品番号
コンポーネント説明
一致するリスト
MAX16823EVKIT Datasheet PDF : 6 Pages
| |||
MAX16823 Evaluation Kit
LEDGOOD Output
The MAX16823 EV kit features an output pad (LEDGOOD)
to monitor the LEDGOOD output logic signal. LEDGOOD
is low when one or more LEDs are open, or when a sig-
nal at any of the DIM inputs remains low for a period
greater than the programmed LEDGOOD delay time.
LEDGOOD output goes low after the programmed
delay period has elapsed. The EV kit delay time is pro-
grammed to 4ms (min) using C4. Refer to the
MAX16823 IC data sheet LEDGOOD section for setting
the LEDGOOD delay time. To adjust the minimum
LEDGOOD delay time, use the following equation:
C4 = tDELAY
257,900(Ω)
where C4 is in farads and tdelay is in seconds.
When shunts are not installed at jumpers JU4, JU6, or
JU7, LEDGOOD is low.
Evaluating External LEDs
at OUT1 and OUT2
The MAX16823 EV kit can be used to evaluate external
LEDs rated up to 70mA at OUT1 and OUT2. Jumpers
JU6 and JU7 configure the EV kit for on-board or exter-
nal LED operation at outputs OUT1 and OUT2. Install
shunts at jumpers JU6 and JU7 to evaluate the EV kit’s
on-board LEDs. To evaluate external LEDs at OUT1,
remove the shunt at JU7. When connecting the external
LEDs at OUT1, connect the anode of the first LED at
OUT1 and the cathode of the last LED at CS1. To eval-
uate external LEDs at OUT2, remove the shunt at
jumper JU6. When connecting the external LEDs at
OUT2, connect the anode of the first LED at OUT2 and
the cathode of the last LED at CS2. See Table 2 for
jumpers JU6 and JU7 configurations.
Table 2. OUT1 and OUT2 LED Operation
(JU6 and JU7)
SHUNT POSITION
EV KIT FUNCTION
Installed
On-board LED operation
Uninstalled*
External LED operation
*LEDGOOD is low when the shunts are removed and external
LEDs are not connected at OUT1 and OUT2.
Evaluating Higher Current LEDs at OUT_3
The MAX16823 EV kit OUT_3 PCB pad can be used to
evaluate LEDs rated for 550mA (typ). A single BJT (Q1)
and resistor R5 provide increased output current capa-
bilities for external LEDs connected at OUT_3.
Jumpers JU4 and JU5 configure OUT_3 for external
LED operation. Jumper JU4 selects on-board or exter-
nal LED operation, while jumper JU5 selects the current
setting for the external LEDs.
To operate the MAX16823 EV kit with the on-board
LEDs, install a shunt across pins 2-3 of jumper JU4,
and remove the shunt from jumper JU5 to set the on-
board LEDs’ (D1, D2, and D3) current to 50mA by
resistor R2.
To operate the MAX16823 EV kit OUT_3 with external
LEDs, install a shunt across pins 1-2 of jumper JU4.
Install a shunt at jumper JU5 to set the external LEDs to
the 550mA (typ) current setting using the parallel resis-
tor combination of R2 and R5. When connecting the
external LEDs at OUT_3, connect the anode of the first
LED to the OUT_3 PCB pad, and the cathode of the last
LED at CS_3. See Tables 3 and 4 for on-board and
external LEDs and current-setting configurations.
Table 3. OUT_3 LED Operation (JU4)
SHUNT
POSITION
OUT3 PIN
EV KIT FUNCTION
1-2
Connects to Q1
External LED operation at
OUT_3
2-3*
Uninstalled*
Connects to D1 On-board LED operation
Open
LEDGOOD = low
*LEDGOOD is low when a shunt is installed at pins 2-3 and
external LEDs are not connected at OUT_3.
Table 4. On-Board or External LED
Current Setting (JU5)
SHUNT
POSITION
CURRENT
SETTING
EV KIT FUNCTION
Not installed
50mA through
resistor R2
On-board LED operation
Installed
550mA through
resistors R2, R5
External LED operation
For proper operation when using higher current external
LEDs at OUT_3, the minimum input voltage must be:
VIN(MIN) = 1.2V + VFT(MAX) + ΔVDO
where 1.2V is the maximum collector-emitter saturation
voltage for the npn transistor Q1, VFT(MAX) is the total
forward voltage of all series-connected LEDs at OUT_3,
and ΔVDO is the MAX16823 dropout voltage from IN to
OUT_.
_______________________________________________________________________________________ 3
Share Link: 