Texas Instruments Evaluation Board for the LM34926 LM34926EVAL/NOPB LM34926EVAL/NOPB Datenbogen
Produktcode
LM34926EVAL/NOPB
+
VOUT2
D1
C4
T1
9.5V
+
+
+
V
IN
BST
RON
RTN
SW
VCC
FB
VIN
VOUT1
R6
R2
R3
C3
C2
C1
R4
R1
UVLO
C6
LM34926
20V-100V
1
2
3
4
5
6
8
7
(TP7)
+
C5
1 F
0.1 F
127
NŸ
8.25
NŸ
130
NŸ
(J1)
UVLO
U1
R5
(J2)
GND
R8
C7
C8
+
D2
EXP
1
NŸ
7.32
NŸ
1 F
0
Ÿ
47 H
0.01 F
1 F
1000 pF
0.1 F
46.4
NŸ
(TP11)
SW
10V
(1:1)
(J3)
IGND
1 F
R10
2
NŸ
R
1
V
IN
(UVLO,rising)
= 1.225V x
R
2
+1
¹
·
©
§
V
IN(HYS)
= I
HYS
R
1
UVLO Threshold and Hysteresis
2
UVLO Threshold and Hysteresis
The UVLO resistors are selected using the following two equations:
(1)
and
(2)
On this evaluation board R1 = 127k
Ω
and R2 = 8.25k
Ω
, resulting in UVLO rising threshold at VIN = 20.5V
and a hysteresis of 2.54V.
2.1
Board Connection and Start-up
The input connections are made using TP1 (VIN) and TP2 (GND) terminals. The primary output appears
at TP3 (VOUT1) and TP4 (GND). The secondary (isolated) output is available across TP5 (VOUT2) and
TP6 (IGND). The input voltage should be gradually increased above UVLO set point of 20.5V. Both the
outputs (VOUT1 and VOUT2) should be close to 10V at this point. This board is designed to function with
input voltage range of 20V to 100V. The minimum VIN threshold can be changed by changing the UVLO
resistors R1, R2. VIN should not exceed 100V.
at TP3 (VOUT1) and TP4 (GND). The secondary (isolated) output is available across TP5 (VOUT2) and
TP6 (IGND). The input voltage should be gradually increased above UVLO set point of 20.5V. Both the
outputs (VOUT1 and VOUT2) should be close to 10V at this point. This board is designed to function with
input voltage range of 20V to 100V. The minimum VIN threshold can be changed by changing the UVLO
resistors R1, R2. VIN should not exceed 100V.
The magnetics in this design is optimized for solution size, and therefore limits the output power. The total
load at the output should not exceed 250mA, otherwise the coupled inductor will
saturate/overheat, which can destroy both the coupled inductor and the regulator IC U1. If a
sustained over-current situation is to be tolerated, a coupled inductor with higher saturation and rms
ratings should be used.
load at the output should not exceed 250mA, otherwise the coupled inductor will
saturate/overheat, which can destroy both the coupled inductor and the regulator IC U1. If a
sustained over-current situation is to be tolerated, a coupled inductor with higher saturation and rms
ratings should be used.
Figure 2. Complete Evaluation Board Schematic
2
AN-2284 LM34926 Isolated Evaluation Board
SNVA675A – August 2012 – Revised April 2013
Copyright © 2012–2013, Texas Instruments Incorporated